Current Opinion in Investigational Drugs

Current Opinion in
Investigational Drugs
Mike Williams EDITOR
Vol 7 No 1 January 2006
Stanley Crooke, Annette Doherty, William Hagmann, John Kemp, Jacob J Plattner CO-EDITORS
In this issue
Central and peripheral nervous system
• The genome: Five years on
• Steroid therapy for exudative age-related
macular degeneration
• Nitrone spin on cerebral ischemia
• Drugs in development for Parkinson's disease
• The mechanism of action of gabapentin in
neuropathic pain
• 5-HT 1A receptor activation in pain relief
• Glycine receptors: A new therapeutic target in
pain pathways
• Does VEGF represent a potential treatment for
amyotrophic lateral sclerosis?
• Ispronicline
• AEOL-10150
• Vivitrex

Current Opinion in Investigational Drugs Vol 7 No 1 January 2006
Editor in Chief Michael Williams USA
Co-Editors Stanley Crooke USA Annette Doherty UK William Hagmann USA John
Kemp GERMANY Jacob J Plattner USA
Patent Editor Hermann AM Mucke AUSTRIA
Thomson Scientific
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Managing Editor
Barbara Chan
Email: barbara.chan@thomson.com
In-house Editors
Tracey Collins (Anti-infectives, Endocrine
and Metabolics, and Oncological)
Email: tracey.collins@thomson.com
Paula Finn (Anti-inflammatory,
Cardiovascular and Renal, and Nervous
System)
Email: paula.finn@thomson.com
Editorial Board
Janet Allen (UK)
Rafael Apitz-Castro (Venezuela)
John F Barrett (USA)
Maria Belvisi (UK)
Frank Bennett (USA)
Andreas Billich (Austria)
Norbert Bischofberger (USA)
Roy Black (USA)
Mel Blumenthal (USA)
Frank Cerasoli (USA)
Bruce Chabner (USA)
Daniel Chu (USA)
Kelvin Cooper (USA)
Joseph Coyle (USA)
Neal Cutler (USA)
Mohsen Daneshtalab (Canada)
Erik De Clercq (Belgium)
Chet De Groat (USA)
Errol DeSouza (Germany)
Andy Dray (Canada)
Mariano Elices (USA)
Jilly Evans (USA)
Tony Evans (Australia)
Giora Feuerstein (USA)
Alan C Foster (USA)
Win Gutteridge (Switzerland)
Jean Marc Herbert (France)
Taff Jones (Canada)
Loran Killar (USA)
Gavin Kilpatrick (UK)
George Koob (USA)
Daniel Lane (USA)
Alan Lewis (USA)
John McCall (USA)
Rodger McMillan (UK)
Heinz Moser (USA)
Bo Öberg (Sweden)
Jose Palacios (Spain)
Alan Palmer (UK)
Michael Parnham (Croatia)
Herbert Pinedo (Netherlands)
Yves Pommier (USA)
John Reed (UK)
Malcolm Richardson (Finland)
Steve Rosenberg (USA)
Alessandro Sette (USA)
Jim Sikorski (USA)
John Souness (USA)
Paul Smith (New Zealand)
Ken Tanaka (USA)
Eugene Thorsett (USA)
Section Editors
January 2006/July 2006
Central and Peripheral Nervous System
Mike Briley (France), Mike Crowell (USA), Robert
Davis (USA), Steve England (UK), Peter
Goadsby (UK), Clifford Woolf (USA), Mike Wyllie
(UK), Stevin Zorn (USA)
February 2006/August 2006
Anti-infectives
Robin Cooper (USA), Simon Croft (Switzerland),
Christian Hubschwerlen (Switzerland), Jeffrey H
Toney (USA), Alan Johnson (UK), Barney
Koszalka (USA), Nicholas Meanwell (USA), Rino
Rappuoli (Italy), John Rex (UK), David A Stevens
(USA)
March 2006/September 2006
Cardiovascular and Renal
Frank Barone (USA), Tom Colatsky (USA), De-Zai
Dai (China), Delvin Knight (USA), Brian Krause
(USA), Keith E Suckling (UK), J Ruth Wu-Wong
(USA)
April 2006/October 2006
Endocrine and Metabolics
Bruno Allolio (Germany), Franklyn Bolander (USA),
Joy Hinson (UK), Nigel Levens (France), Terry
Opgenorth (USA)
May 2006/November 2006
Anti-inflammatory, Immunologicals and
Biologicals
Cynthia Darlington (New Zealand), Francis Dumont
(USA), David Howat (France), Cees Korstanje
(Netherlands), Tony Manning (USA), Randall Morris
(USA), Neville Punchard (UK)
June 2006/December 2006
Oncological
Suresh Ambudkar (USA), Andrew Dorr (USA),
David Gewirtz (USA), Michael Lotze (USA), Alain
Rolland (USA), Edward Sausville (USA), Ian
Stratford (UK), Mario Sznol (USA), Paul
Workman (UK)

Current Opinion in Investigational Drugs
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Aims and organization
Current Opinion in Investigational Drugs is a monthly publication covering all therapeutic areas, in recognition of the
increasingly multi-disciplinary nature of modern drug discovery and development. With Current Opinion in Investigational
Drugs, we aim to help the reader by providing in a systematic manner:
• critical reviews of selected areas of investigational drug research
• expert evaluation of selected drugs currently in clinical trials
• selection of the most interesting papers and patents, annotated by experts.
Subject division
Six therapeutic categories are covered with each being featured in separate journal issues, and each therapeutic area being
covered twice-yearly. The broad therapeutic categories and the specialist topics within each are as follows:
• Anti-infectives Antifungals and antiparasitics; antibacterials (β-lactams, glycopeptides and other agents); antibacterials
(quinolones, macrolides and oxazolidinones); vaccines; antivirals (HIV); antivirals (non-HIV)
• Anti-inflammatory, Immunologicals and Biologicals Musculoskeletal; respiratory; dermatology; nervous system;
transplantation
• Cardiovascular and Renal Hypertension and renal failure; stroke and angina; arrhythmia and heart failure;
antithrombotics; hemostasis and hematological diseases; atherosclerosis, hypercholesterolemia and heart disease
• Endocrine and Metabolics Diabetes, reproductive endocrinology, hormone disorders, bone metabolism and obesity
• Central and Peripheral Nervous System Pain; neuro-urology and neurogastroenterology; neurodegenerative and
cognitive disorders; affective/behavioral/personality disorders and substance abuse; neurology and neuroprotection;
schizophrenia and psychosis
• Oncological Cell signaling modulators; cytotoxic drugs; immunotherapeutic drugs and monoclonal antibodies; protein
therapeutics, including growth factors; gene therapy; antisense inhibitors
Each issue also contains a general alerts section which covers all therapeutic areas.
Selection of topics to be reviewed Section Editors, who are major authorities in the field, are appointed by the Editors of
the journal. They divide their section into a number of topics, ensuring that the field is comprehensively covered and that all
issues of current importance are emphasized. Section Editors commission reviews from authorities on each topic that they
have selected. Section Editors also identify compounds of significant promise and commission expert evaluations of these
drugs. Submitted articles are peer reviewed before publication.
Contents
Patent alerts Brief commentaries on the scientific and/or commercial significance of new patents selected and written by
experts within their respective fields. These are presented beside the patent abstract from Patent fast-alert, published by
Thomson Current Drugs.
Paper alerts Expert commentary on a selection of recently published papers is provided.
Therapeutic overviews Short mini-reviews in which an area of interest to the pharmaceutical industry is critically reviewed in
the context of recent developments. These pieces are intended to be personal, thought-provoking and controversial, where
appropriate.
Reviews Authors write concise reviews in which they present recent developments in their subject, emphasizing the aspects
that, in their opinion, are most important and provide short annotations to the papers and patents that they consider to be the
most interesting from all those recently published in their topic. The reviews focus predominantly on investigational drugs, or
the therapeutic/commercial applications of new discoveries.
Drug evaluations Expert commentary on the scientific and commercial potential of selected drugs in clinical trials are
provided in each issue, in the form of drug evaluations. An evaluation is a review of the available literature (scientific and
commercial) and acts as an expert guide to the bibliography, highlighting references of particular interest. Opinion on the
drug's potential, with a personal viewpoint on its therapeutic and economic viability, are included. The bibliographies contain
only those papers referenced in the report, but readers may purchase the full bibliography, as it appears in Current Drugs'
Investigational Drugs database (IDdb), if they wish.
Literature classifications Key references relating to the drug are classified according to a set of standard headings to
provide a quick guide to the bibliography. These headings are as follows:
Chemistry: References which discuss synthesis and structure-activity relationships.
Metabolism: References which discuss metabolism, pharmacokinetics and toxicity.
Biology: References which disclose aspects of the drug's pharmacology in animal models.
Clinical: Reports of clinical phase studies in volunteers providing, where available, data on the following: whether the
experiment is placebo-controlled or double- or single-blind, number of patients, dosage.
Literature annotations Throughout the journal, a bulleting system is used to denote information deemed by the author or
editor to be either: • of special interest; or •• of outstanding interest.
Bi-annual indexes Every six months, following completion of coverage of each therapeutic area, cumulative indexes of
contents are provided.

Current Opinion in Investigational Drugs Vol 7 No 1 January 2006
Paper alert
1 Mohsen Daneshtalab, Mariano J Elices & Robert E Hurst
Patent selection
4 Hermann AM Mucke
Patent alert
7 Hermann AM Mucke, Peter Norman & Clifford Whelan
Central and Peripheral Nervous System
Mike Briley, Mike Crowell, Robert Davis, Steve England,
Peter Goadsby, Clifford Woolf, Mike Wyllie & Stevin Zorn
14 Michael Williams
Editorial overview: The genome: Five years on
18 Maneli Mozaffarieh & Andreas Wedrich
Editorial overview: Steroid therapy for exudative age-related
macular degeneration: Bridging the gap until a cure is found
20 Sheila A Doggrell
Nitrone spin on cerebral ischemia
25 Tom H Johnston & Jonathan M Brotchie
Drugs in development for Parkinson's disease: An update
33 J Kenneth Baillie & Ian Power
The mechanism of action of gabapentin in neuropathic pain
40 Francis C Colpaert
5-HT1A receptor activation: New molecular and neuroadaptive
mechanisms of pain relief
48 Joseph W Lynch & Robert J Callister
Glycine receptors: A new therapeutic target in pain pathways
54 Joanna Iłżecka
Does VEGF represent a potential treatment for amyotrophic
lateral sclerosis?
60 Hugo Geerts
Ispronicline (Targacept)
70 Richard W Orrell
AEOL-10150 (Aeolus)
81 Christine E Heading
Vivitrex (Alkermes/Cephalon)
89 Erratum

The next issue of this journal (Vol 7 No 2 February 2006)
Will contain:
Anti-infectives
Robin Cooper, Simon Croft, Christian Hubschwerlen, Jeffrey H
Toney, Alan Johnson, Barney Koszalka, Nicholas Meanwell, Rino
Rappuoli, John Rex & David A Stevens
Barney Koszalka & Nicholas Meanwell
Editorial overview: Viral entry mechanisms
Mark Erion
HepDirect prodrugs for targeting nucleotide-based antiviral drugs to
the liver
Asim Kumar Debnath
Prospects and strategies for the discovery and development of
small-molecule inhibitors of six-helix bundle formation in class 1 viral
fusion proteins
Robert Smolic, Martina Volarevic, Catherine H Wu & George Y
Wu
Potential applications of siRNA in hepatitis C virus therapy
Larry Boone
Next generation non-nucleoside reverse transcriptase inhibitors for
the treatment of HIV
Maria Zambon
Influenza immunization strategies
David Koelle
Novel treatment options for herpes simplex virus
Ursula Theuretzbacher & Jeffrey H Toney
Nature's clarion call of antibacterial resistance: Are we listening?
David Shlaes
Novel tetracyclines
David Kaufman
Veronate (Inhibitex)
Joseph Jao-Yiu Sung & Henry Lik-Yuen Chan
HBV-ISS (Dynavax)
David McMillan
StreptAvax (ID Biomedical)

Paper alert
A selection of interesting recently published papers from
major journals relating to drug discovery and research.
Current Opinion in Investigational Drugs 2006 7(1):1-3
© The Thomson Corporation ISSN 1472-4472
Contents
1 Anti-infectives
2 Endocrine & metabolic
2 Oncological
Anti-infectives
Selected by Mohsen Daneshtalab (Memorial University, St
John's, NL, Canada)
In vitro and in vivo antibacterial activities of SM-216601, a
new broad-spectrum parenteral carbapenem.
Ueda Y, Kanazawa K, Eguchi K, Takemoto K, Eriguchi Y,
Sunagawa M (Sumitomo Pharmaceuticals Research Division,
Osaka, Japan).
Antimicrob Agents Chemother (2005) 49(10):4185-4196.
•• Significance The emergence of multidrug-resistant, Grampositive
bacteria such as methicillin-resistant Staphylococcus
aureus (MRSA), penicillin-resistant Streptococcus pneumoniae
(PRSP) and vancomycin-resistant enterococci (VRE), has
affected the usefulness of antibacterial chemotherapy in recent
years. Resistance to β-lactam antibiotics is a serious concern
because this class of compounds exhibits several advantages
over other antibacterials. Thus, there is an urgent need for new
β-lactam agents effective against resistant pathogens. These
researchers previously reported that 2-(4-arylthiazole-2-ylthio)-
1β-methylcarbapenems, such as SM-17466 (Sumitomo Seika
Chemicals Co Ltd/F Hoffmann-La Roche Ltd) and its
derivatives, showed potent activity against MRSA owing to
their high affinity for penicillin-binding protein (PBP)2a.
SM-17466 was also effective against Enterococcus faecium
compared with other carbapenems. These observations
prompted the search for novel carbapenems with potent
activity against MRSA and VRE. SM-216601 (Sumitomo Seika
Chemicals Co Ltd/F Hoffmann-La Roche Ltd), a
dihydropyrrolyl thiazole analog of SM-17466, was identified,
which demonstrated broad-spectrum antibacterial activity
against Gram-positive and Gram-negative bacteria. This paper
describes in vitro studies investigating the activity of SM-216601
against different clinical isolates compared with vancomycin,
linezolid and several other β-lactams. In addition, the efficacy of
SM-216601 against systemic infections in mice caused by
methicillin-sensitive S aureus, MRSA, Escherichia coli,
Pseudomonas aeruginosa and experimental E faecium
subcutaneous abscesses is described.
Findings This study investigated the in vitro antibacterial
activity, affinity for bacterial PBPs and resistance to
hydrolysis by dehydropeptidase (DHP)-1 of SM-216601, and
evaluated its in vivo efficacy against Gram-positive and
Gram-negative bacteria and pharmacokinetics in mice.
SM-216601 exhibited potent activity against MRSA, PRSP,
VRE, ampicillin-resistant Haemophilus influenzae, Moraxella
catarrhalis, E coli, Klebsiella pneumoniae and Proteus mirabilis.
In addition, SM-216601 was highly efficacious against
experimentally induced infections in mice caused by
S aureus, E faecium, E coli and P aeruginosa. Its sensitivity against
renal DHP-1 was similar to that of meropenem and superior to
that of imipenem. SM-216601 exhibited improved
pharmacokinetics compared with imipenem and meropenem
in mice, rats, dogs and cynomolgus monkeys.
Design, synthesis, and biological activity of m-tyrosinebased
16- and 17-membered macrocyclic inhibitors of
hepatitis C virus NS3 serine protease.
Chen KX, Njoroge FG, Pichardo J, Prongay A, Butkiewicz N, Yao
N, Madison V, Girijavallabhan V (Schering-Plough Research
Institute, Kenilworth, NJ, USA).
J Med Chem (2005) 48(20):6229-6235.
• Significance The worldwide spread of hepatitis C virus
(HCV) infection has caused a global health crisis. The only
therapies currently available for the treatment of HCV infection
are subcutaneous interferon (IFN)α or pegylated IFNα
monotherapy, or the combination of IFNα or pegylated IFNα
and oral ribavirin. These therapies have limited efficacies and
cause considerable side effects in patients. Therefore, the search
for small molecules with high efficacy and less toxicity
continues. The viral NS3 protein and its corresponding enzyme,
NS3 protease, are attractive drug targets in HCV. Many
protease inhibitors that have peptidic molecular structures have
been developed in recent years. However, because of low
bioavailability and poor pharmacokinetics, most of these
inhibitors have failed to make it onto the market.
Peptidomimetics are peptidic analogs that resist hydrolytic
enzymes while exhibiting the same enzyme inhibitory
characteristics as the corresponding peptides. The potential of
cyclic hexapeptides as inhibitors of the HCV NS3 protease have
been reported in a number of studies. Based on these
discoveries, novel 16- and 17-membered ring analogs were
synthesized and evaluated for HCV NS3 protease inhibitory
activity.
Findings The synthesis of these cyclic peptides began with
the coupling of the commercially available N-Boccyclohexylglycine
and m-tyrosine methyl ester, which in five
steps gave rise to methyl 11(S)-cyclohexyl-9.12-dioxo-2-oxa-
10,13-diazabicyclo[14.3.1]eicosa-1(20),16,18-triene-14(S)carboxylate.
Hydrolysis of this intermediate followed by
coupling with [2-(3-amino-2-hydroxy-hexanoylamino)acetylamino]-phenylacetic
acid tert-butyl ester hydrochloride
afforded the desired 17-membered macrocyclic compounds
as either O-tert-butyl ester, free carboxylic acid, or the
corresponding mono- or dimethylamide analogs. The
corresponding 16-membered analogs were synthesized in
the same manner as above. In an HCV protease continuous
assay, the 16-membered analogs were less active than the
corresponding 17-membered analogs. This study confirmed
the potential of these 17-membered macrocycles as lead
compounds for further development of anti-HCV drugs.
Synthesis and structure-activity relationships of novel
anti-hepatitis C agents: N 3 ,5'-cyclo-4-(β-D-ribofuranosyl)vic-triazolo[4,5-b]pyridin-5-one
derivatives.
Wang P, Du J, Rachakonda S, Chun B-K, Tharnish PM, Stuyver
LJ, Otto MJ, Schinazi RF, Watanabe KA (Pharmasset Inc,
Princeton, NJ, USA).
J Med Chem (2005) 48(20):6454-6460.
• Significance Chronic hepatitis C virus (HCV) infection is
1

2 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
predicted to become a major challenge for healthcare providers,
especially as the currently asymptomatic carriers of this virus
may develop hepatocellular carcinoma. Furthermore, the death
rate due to HCV infection is predicted to triple in the next ten to
20 years. Current treatment protocols involve either the
administration of interferon (IFN)α or its pegylated form alone
or in combination with ribavirin (RBV). IFNα causes
neuropsychiatric adverse effects and anemia is the most
common side effect of RBV. In addition, the response rate for
both therapeutic approaches is < 50%. Thus, the identification
of new and effective drugs for the treatment of HCV infection is
critical. These researchers previously identified a novel
compound, N 3,5'-cyclo-4-(β-D-ribofuranosyl)-vic-triazolo[4,5b]pyridin-5-one
(CRTP), which exhibited moderate anti-HCV
activity in a subgenomic RNA replicon system. In an effort to
discover more potent anti-HCV agents, a series of 6- and 7substituted
derivatives of CRTP were synthesized. In this
study, different 5-thiono, 6-halo, 7-alkylamino and 7-methyl
analogs of CRTP were synthesized and their anti-HCV activity
and cytotoxicity evaluated. Some of the newly synthesized
compounds exhibited 8- to 40-fold more potent anti-HCV
activity than that of CRTP.
Findings CRTP was initially synthesized from 1-(2,3,5-tri-Obenzoyl-β-D-ribofuranosyl)-5-nitropyridin-2-one
using either
a five-step traditional synthetic method or a one-pot
synthetic method. Further synthetic procedures involving
CRTP resulted in 5-thiono, 6-chloro/bromo, 7-amino or 7alkylamino
analogs. The 7-methyl analog of CRTP was
prepared using a different methodology. The synthesized
compounds were tested for their ability to inhibit HCV RNA
in a subgenomic replicon Huh-7 cell line. Cytotoxicity was
determined using an MTS assay. Among the compounds
tested, the 5-thiono, 6-chloro, 6-bromo, 7-amino, 7methylamino
and 7-methyl analogs exhibited more potent
anti-HCV activity than CRTP, with the 6-chloro and 6-bromo
analogs being the most potent. This study suggests a direct
correlation between the anti-HCV activity and the
cytotoxicity of these compounds.
Endocrine & metabolics
Selected by Mariano J Elices (PharmaMar USA, Cambridge,
MA, USA)
Normal fasting plasma glucose levels and type 2
diabetes in young men.
Tirosh A, Shai I, Tekes-Manova D, Israeli E, Pereg D, Shochat
T, Kochba I, Rudich A; Israeli Diabetes Research Group
(Medical Corps Headquarters, Tel-Hashomer, Israel).
N Engl J Med (2005) 353(14):1454-1462.
• Significance Science textbooks generally list the range of
fasting plasma glucose values for healthy individuals
(normoglycemic) as being 70 to 110 mg/dl. However, in
2003, an expert committee at the American Diabetes
Association (ADA) revised this long-held view and
suggested that fasting blood glucose levels of 101 to 109
mg/dl represent impairment of glucose metabolism and
thus pose a risk for the development of type 2 diabetes. In
general, the incidence of type 2 diabetes has increased in
developed countries, including among younger members of
the population that have traditionally not been considered to
be at risk; thus it is of significant value to uncover risk
factors for this illness.
Findings In order to address which risk factors contribute to
the development of type 2 diabetes, the investigators examined
a computerized database that was established in 1992 to
capture data from the MELANY (MEtabolic, Lifestyle, And
Nutrition assessment in Young adults) trial. This trial was
conducted among military personnel over 25 years of age in
Israel who received periodic examinations every three to five
years. At the time of their periodic visit, each individual gave a
blood sample after a 14-h fasting period, and received a medical
examination; a detailed questionnaire was also completed by
each individual. The primary endpoint of the study was a new
diagnosis of type 2 diabetes during the trial (based on criteria
outlined by the ADA expert committee) which involved the
recording of two fasting plasma glucose levels of at least 126
mg/dl. Of 13,163 male individuals with fasting blood glucose
levels of ≤ 100 mg/dl, there were 208 new cases of type 2
diabetes (ie, a 1.6% incidence) spanning an average of 5.7 years
of follow-up. Multivariate models showed that males with
fasting blood glucose at the high end of the normal range (91 to
99 mg/dl), combined with serum triglyceride levels of ≥ 150
mg/dl, had an 8.23-fold higher risk of developing type 2
diabetes compared with individuals with fasting plasma
glucose and serum triglyceride levels of ≤ 86 and < 150 mg/dl,
respectively. In a similar manner, hazard ratios revealed a 8.29fold
higher risk of developing type 2 diabetes in obese men
(body mass index ≥ 30) even when they had a normal, albeit
high, fasting blood glucose (91 to 99 mg/dl), compared with
control individuals with fasting plasma glucose levels and a
body mass index of ≤ 86 mg/dl and < 25, respectively. These
data strongly suggest that normoglycemic individuals with
either serum triglyceride levels > 150 mg/dl or exhibiting
relative obesity (ie, body mass index ≥ 30) are at an increased
risk of developing type 2 diabetes later in life. From a healthcare
standpoint, these findings expose a host of opportunities in
diagnostic, preventive and therapeutic areas in type 2 diabetes.
Oncological
Selected by Robert E Hurst (Oklahoma University Health
Sciences Center, OK, USA)
A potential synergistic anticancer effect of paclitaxel
and amifostine on endometrial cancer.
Dai D, Holmes AM, Nguyen T, Davies S, Theele DP,
Verschraegen C, Leslie KK (University of New Mexico Health
Sciences Center, Albuquerque, NM, USA).
Cancer Res (2005) 65(20):9517-9524.
• Significance Although the prognosis for endometrial cancer
is generally good, advanced or recurrent cases have a poor
prognosis, with chemotherapy offering mostly palliative
therapy. Amifostine has been proven to protect normal cells
against a number of chemotherapeutic agents, including
paclitaxel. Amifostine not only allows the administration of
higher doses of paclitaxel but, in this study, the drug also had a
direct effect on endometrial cancer cells, and acted
synergistically with paclitaxel. Thus, combination therapy
with these two drugs may be more effective than paclitaxel
alone.

Findings In vitro studies with poorly differentiated Hec50co
endometrial cancer cells demonstrated that amifostine had
direct anticancer effects, producing G1 arrest of the cell cycle
and inducing apoptosis. Amifostine was also active in a
flank xenograft model in nude mice. A single dose of
Paper alert 3
amifostine (178 µM) reduced the IC50 value of paclitaxel
from 14 to 2 nM, and amifostine acted synergistically with
paclitaxel to induce G2 to M growth arrest and apoptosis.
The survival of mice was improved significantly over either
agent alone in a flank xenograft model.

4
Patent selection
The following recently issued patents have been pre-selected
as being of particular interest from the Current Patents
Gazette. Full alerts will appear in forthcoming issues of
Current Opinion in Investigational Drugs.
Current Opinion in Investigational Drugs 2006 7(1):4-6
© The Thomson Corporation ISSN 1472-4472
Oncologic, endocrine and metabolic
NOVARTIS AG Inhibitors of IAP. WO-2005097791 (20
October 2005)
• Compounds that inhibit the binding of Smac protein to
inhibitors of apoptosis proteins (IAPs), thereby promoting the
apoptosis of rapidly dividing cells are described. These
compounds are useful for the treatment of proliferation diseases
such as cancer. This application represents continuation of
research by this group on Smac and IAPs (see also WO-
2004005248 and WO-2005074989); a May 2005 press release
from Novartis gives details of the Smac mimetic project. Some
of the inventors have previously worked on kinase inhibitors
and integrin receptor antagonists.
UNIVERSITY OF WESTERN AUSTRALIA Osteoblast growth
factor. WO-2005100389 (27 October 2005)
• Caltrin (calcium transport inhibitor), a small cysteine-rich
secretory protein isolated from a hematopoietic macrophage
cell line, elevates cytosolic calcium levels and may be used
for treating or preventing bone disorders. The inventors are
named on prior applications from Verigen Transplantation
Service International AG, for example, WO-03026689,
concerning the use of growth factors from chondrocytes for
the treatment of osteogenesis.
MEDIQUEST THERAPEUTICS INC Polyamine analogs that
activate antizyme frameshifting. WO-2005105729 (10
November 2005)
• Polyamine analogs that activate antizyme frameshifting to
downregulate production of endogenous polyamines by
ornithine decarboxylase and transport via the corresponding
polyamine transporter are claimed. These compounds are
useful in the treatment of cellular proliferation-associated
indications, particularly alopecia. This application claims
several polyamines, of which two compounds have previously
been specifically claimed in US-06914079 (by the same
inventors). MediQuest, in collaboration with researchers at the
University of Utah, is investigating a series of polyamine
analogs. The company is also investigating a polyamine
transporter inhibitor ORI-1202.
PFIZER INC Inhibitors of checkpoint kinases (Wee1 and
Chk1). US-20050250836 (10 November 2005)
• Novel substituted indacene molecules that specifically inhibit
one or both of the checkpoint kinases Wee1 and Chk1 and are
useful in the treatment of proliferative disorders are described.
Pfizer is investigating PD-166285, a protein kinase inhibitor.
Results presented at the American Association for Cancer
Research meeting in April 2000 indicated that PD-166285
inhibited Wee1 tyrosine kinase. Pfizer (formerly Agouron) is
also investigating a series of Chk1 inhibitors for the potential
treatment of cancer. As of May 2005, investigations were
ongoing (see WO-03091255).
SMITHKLINE BEECHAM CORP; CYTOKINETICS INC Certain
chemical entities, compositions, and methods. WO-
2005107762 (17 November 2005)
• Substituted heterocyclic amides as inhibitors of CENP-E
kinesin activity for the treatment of cellular proliferative
disorders are described. This continues the collaboration
between Cytokinetics and GlaxoSmithKline (formerly
SmithKlineBeecham), although this appears to be a new
research direction as previous research relates to KSP
kinesin (see WO-2005060692, which names three of the
present inventors). Cytokinetics and GlaxoSmithKline have
two KSP inhibitors in phase I and II trials for cancer.
BUCK INSTITUTE; TOURO UNIVERSITY; THE BURNHAM INSTITUTE
Artificially designed pore-forming proteins with
antitumor effects. US-20050256040 (17 November 2005)
• Use of a small globular protein (SGP) to disrupt a biological
membrane is claimed. SGP is established as the prototype for a
new class of artificial proteins designed for therapeutic
application. SGP can be used for disrupting tumor growth (eg,
Kaposi's sarcoma, breast carcinoma, malignant melanoma of
the skin, lung and prostate cancer and metastases). This
application continues the inventors' cancer research (eg, WO-
2005094383). One of the inventors is associated with the
Burnham Institute and the other with the University of Touro.
E MERCK PATENT GMBH GM3 synthase as a therapeutic
target in microvascular complications of diabetes. WO-
2005108600 (17 November 2005)
• GM3 synthase inhibitors to treat microvascular complications
of diabetes (eg, diabetic nephropathy) are claimed. Also claimed
is a method for screening for GM3 synthase inhibitors. See also
WO-00234201 and WO-09936396 for previous applications
by members of this team.
Pulmonary-allergy, dermatological,
gastrointestinal and anti-inflammatory
ONO PHARMACEUTICAL CO LTD Novel BLT2-mediated
disease, and BLT2 binding agent and compound. WO-
2005102388 (03 November 2005)
• A compound capable of selective binding to BLT2 is
disclosed. Its use as a therapeutic agent for BLT2-mediated
disease, including cutaneous disorders, bowel disease and
HIV infection, is described. This application may be related
to the company's ONO-4057, a dual antagonist of two
leukotriene B4 receptors, BLT1 and BLT2, for the potential
treatment of Behcet's disease, psoriasis and inflammatory
bowel disease. WO-2004031118 (by different inventors) is
cited as relevant in the search report.
NOVARTIS AG CRTH2 receptor antagonists. WO-
2005105727 (10 November 2005)
• Novel compounds as CRTH2 (G-protein-coupled
chemoattractant receptor expressed on Th2 cells) receptor
antagonists, useful for the treatment of respiratory and
inflammatory conditions, are disclosed. CRTH2 appears to
be a new target for Novartis and the inventors, this being
their only patent application on the receptor. Oxagen and
Ortho-McNeil are currently leading this field, with both
companies having programs in preclinical development.

Anti-infectives
JANSSEN PHARMACEUTICA NV Inhibitors of bacterial type III
protein secretion systems. US-20050250819 (10
November 2005)
• Novel triazine compounds as inhibitors of bacterial type III
protein secretion systems, useful for the treatment and
prevention of bacterial infections, particularly Gramnegative
bacterial infections, are described. The inventors
have been named on other applications disclosing
antibacterials. However, this specific action appears to be a
new target.
Biological and immunological
CATALYST BIOSCIENCES INC Cleavage of VEGF and VEGF
receptor by wild-type and mutant proteases. WO-
2005100556 (27 October 2005)
• Mutated granzyme B polypeptides (muteins) that cleave
vascular endothelial growth factor (VEGF) or the VEGF
receptor and inhibit angiogenesis are claimed. The muteins
may be used for the treatment of angiogenesis-related
disorders (eg, cancer, inflammation, diabetes and macular
degeneration). This is only the company's second
application and continues its development of modified
enzymes (see WO-2004031733). In July 2005, Catalyst
exclusively licensed intellectual property covering protease
engineering from Torrey Pines.
CURTIN UNIVERSITY OF TECHNOLOGY Therapeutic heparins
and their binding to interleukins 4 and 5, and PECAM-1.
WO-2005100374 (27 October 2005)
• These glycosaminoglycan oligosaccharides are claimed for
use in the treatment of a wide range of conditions. The
British inventor appears to be based at the National
Institute for Biological Standards and Control.
Bassiri A, Das A, Dillon S, Duffy K, Seideman J, Mbow ML,
Karlsson L, Sun S, Zhu J, Cunningham M Toll-like receptor
9 effector agents and uses thereof. US-20050244410 (03
November 2005)
• Cell-surface toll-like receptor 9 (TLR9) effector agents, such
as TLR9 receptor binding agents and TLR9 ligand binding
agents (namely antibodies and other proteins), and their use
in modulating immune responses for the treatment of, for
example, infections, cancer and inflammation, are described.
The inventors appear to be based at Centocor and feature on
a related application, WO-2004096156.
E MERCK PATENT GMBH Dihydrobenzothiophenes. WO-
2005108355 (17 November 2005)
• Dihydrobenzothiophenes as modulators of mitotic motor
proteins, particularly Eg5, useful for the treatment of, for
example, angiogenesis, cancers, arteriosclerosis, eye
disorders and inflammation, are disclosed. See WO-
2005063735 for substituted tetrahydroquinoline derivatives
with the same action.
Central and peripheral nervous system
Patent selection 5
BIOCORTECH Derivatives of 14,15-dihydro 20,21dinoreburnamenin-14-ol,
and applications thereof. WO-
2005103047 (03 November 2005)
• 14,15-Dihydro 20,21-dinoreburnamenin-14-ol derivatives
are targeted at the treatment of depression. A similar use of
the parent nucleus was claimed in WO-2005082365. This
application is possibly linked to BC-19, an orally active
small molecule believed to reactivate the norepinephrine
pathways, which Biocortech is developing for the potential
treatment of depression. By April 2005, phase II trials of
BC-19 were underway.
SANGAMO BIOSCIENCES INC Treatment of neuropathic pain
with zinc finger proteins. WO-2005100392 (27 October
2005)
• Use of a nucleic acid consisting of a zinc finger DNAbinding
domain engineered to bind target genes and
modulate overexpression of dorsal root ganglia genes (eg,
VR1, TRKA and Nav1.8) of pain patients, and a
transcriptional repression domain, are described. This
application appears to be related to the company's ZFP TF
(pain) gene therapy, using Avigen's adeno-associated virus
gene delivery system for the potential treatment of
neuropathic pain. See US-20040091991 and WO-
2005028630.
ELI LILLY & CO BACE inhibitors. WO-2005108358/WO-
2005108358 (17 November 2005)
• Alkylamide-substituted pyrrolidine and related
ethanolamine derivatives are disclosed. These compounds
are β-amyloid precursor protein cleaving enzyme (BACE)
inhibitors, and appear to be some of the first small molecules
to emerge from the program. See WO-00068266 and WO-
00069262 for related drug screening methods and
technology. Lilly is investigating ethanolamine-containing
peptide-based BACE inhibitors, including LY-2070103, for
the potential treatment of Alzheimer's disease. In August
2005, one of the inventors from this team presented
preclinical data from this program at the 230th American
Chemical Society meeting in Washington DC.
Cardiovascular, ocular and renal
ARYX THERAPEUTICS INC New 4-hydroxycoumarin
derivatives are vitamin K epoxide reductase inhibitors -
useful for the treatment of coagulation disorders. WO-
2005100336 (27 October 2005)
• 3-Substituted 4-hydroxy-2-oxo-2H-chrom-3-ene derivatives
are claimed. See WO-02085882 for related warfarin
analogs. ARYx is investigating ATI-5000, a warfarin
analog identified using its RetroMetabolic platform
technology, for the potential treatment of deep vein
thrombosis and prevention of stroke in atrial fibrillation
patients.

6 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
JAPAN HEALTH SCIENCE FOUNDATION; UNIVERSITY OF
TOKUSHIMA Agent for controlling cholesterol
homeostasis-associated gene transcription activity
mediated by FXR activation. WO-2005097097 (20 October
2005)
• Two of the inventors are based at Tokushima Bunri
University, and all are named on WO-2005092328, which
disclosed bis(bibenzyl) cyclic ether derivatives as farnesoid
X-receptor (FXR) activators, useful for the treatment of
hyperlipidemia.
THERAPTOSIS SA Caspase-2 inhibitors and their biological
applications. WO-2005105829 (10 November 2005)
• Novel caspase-2 inhibitors and their use for treating
ischemia are claimed. Several of these inventors claimed
double-stranded RNA molecules with this activity in WO-
2004103389.

Patent alert
Patent alert provides abstracts and expert commentary on a
selection of recent patents that have been identified as being
of particular interest. Selections are based on patent abstracts
featured in patent products published by Thomson
Scientific. Current opinions are provided based on the
novelty of the invention and its potential application.
Current Opinion in Investigational Drugs 2006 7(1):7-13
© The Thomson Corporation ISSN 1472-4472
Contents
7 Anti-inflammatory & immunomodulatory
8 Cardiovascular & renal
9 Central & peripheral nervous system
10 Endocrine & metabolics
12 Oncological
Anti-inflammatory & immunomodulatory
Selected by Clifford Whelan (Phlogopharm Ltd, Hatfield,
Hertfordshire, UK)
New C5a receptor inhibitory compounds - useful for
treating, eg, inflammation and S aureus infections
ALLIGATOR BIOSCIENCE AB (PUBL) (Van Strijp JAD, De Haas
CJC, Kemmink J, Van Kessel KPM)
WO-2005100385, 27 October 2005
Compounds for preventing intramolecular contact of Nterminal
residues 10 to 18 of human C5aR with the extracellular
loops, are claimed. Also claimed are further compositions and
use of the compounds for treating conditions involving the C5a
receptor on cells other than neutrophils, monocytes and
endothelial cells, for example, inflammation, and for use in
therapeutic vaccines for infections caused by chemotaxis
inhibitory protein from Staphylococcus aureus (CHIPS)producing
bacteria. The agents are stated to be small enough for
use in therapy. U937 cells expressing C5aR were incubated with
increasing concentrations of CHIPS31-121 or CHIPS31-121
mutant compounds. The samples were further incubated with
10 µg/ml of FITC-labeled anti-C5aR S5/1 monoclonal antibody.
The IC50 values of the CHIPS31-121 mutants, in which single
amino acids were substituted into alanines, were calculated.
The CHIPS31-121 mutants with the lowest IC50 values (ng/ml)
were N47 (5), R46 (10), Y121 deleted (10), K54 (10), K50 (10),
G102 (12) and K101 (15). Chemical sequences are provided in
the source document.
Current Opinion
S aureus is a common member of the bacterial flora on human
skin. Although its presence is usually symptom free, it can
cause a number of pathologies, ranging from superficial
pustules to major life-threatening infections. Furthermore, the
evolution of strains of S aureus that are resistant to antibiotic
therapy makes the development of novel approaches to the
treatment of infection an important therapeutic target.
Neutrophil accumulation at the site of inflammation and
infection is a hallmark of acute inflammation. Neutrophil
chemotaxis can result from a wide range of compounds and
this may have physiological importance. However, major
chemoattractants in acute inflammation are complement
products formed from plasma protein. This disclosure describes
a series of proteins that inhibit binding of the complement
product C5a to its receptor. The proteins described are based on
an endogenous protein released by S aureus. Such proteins are
likely to reduce neutrophil accumulation in vivo and may even
be of benefit in inflammatory diseases, such as chronic
obstructive pulmonary disease, in which products released by
activated neutrophils appear to initiate changes that are not
beneficial. However, in infection, particularly that characterized
by abscess formation, neutrophil chemotaxis appears to contain
the infection, and patients who are deficient in complement
products seem to suffer severe infections. Thus, further research
is required to determine whether the proteins described will
have utility in the treatment of infection, and to determine how
they can be utilized as anti-inflammatory agents.
New imidazole compounds are H4 receptor inhibitors -
useful for the inhibition of leukocyte recruitment and for
the treatment of inflammation and immune disorders
JANSSEN PHARMACEUTICA NV (Buzard DJ, Edwards JP,
Kindrachuk DE, Venable JD)
WO-2005092066, 06 October 2005
New imidazole compounds are claimed, as well as their use
as H4 receptor inhibitors for the inhibition of leukocyte
recruitment and for the treatment of inflammation. The
compounds are claimed to be useful for the treatment of
inflammatory response (eg, to chemotherapy or infection),
allergy, dermatological disorders, autoimmune disease,
lymphatic disorders, immunodeficiency, asthma, chronic
obstructive pulmonary disease, atherosclerosis, rheumatoid
arthritis, multiple sclerosis and inflammatory bowel disease
(eg, Crohn's disease or ulcerative colitis). The compounds
can also be isotopically labeled and used in diagnostic
imaging. No suitable advantage is given. The illustrated
compound had a Ki value of 6 nM when tested in vitro for its
ability to bind to human histamine H4 receptors expressed
by SK-N-MC or COS7 cells. Seventy specific compounds are
claimed, including 1-(3-[4-[4,5-bis-(3-methoxyphenyl)-1Himidazol-2-yl]-3-chlorophenoxy]propyl)-4-methyl[1,4]diazepane.
C
H 3
O
O CH3
H
N
Cl O
N
WO-2005092066
(Janssen)
Current Opinion
Leukocyte accumulation is one of the hallmarks of
inflammation. Generally in the lesion, granulocytes and
macrophages act as effector cells and lymphocytes act to
orchestrate the response. Many reports in the literature suggest
N
N
CH 3
7

8 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
that histamine may have a role in the process of leukocyte
recruitment by acting on leukocytes to promote chemotaxis,
and by acting on endothelial cells to increase P-selectin
expression and promote leukocyte adhesion. Until recently,
research in this area was unclear, partly because the histamine
receptors mediating these events were not well defined. The
finding that leukocytes, such as eosinophils, express histamine
H4 receptors that mediate histamine-induced chemotaxis has
provided researchers with an additional therapeutic target that
this disclosure seeks to exploit.
Eosinophils are thought to be the effector cells responsible for
the inflammatory changes that underlie asthma, atopic
dermatitis and other pathologies. Thus, it seems reasonable to
propose that compounds that inhibit eosinophil accumulation
in tissues will have therapeutic utility. However, a degree of
redundancy exists in the inflammatory process, which may
enable the body to mount a response in the absence of one
pathway. The same appears to be the case with eosinophil
recruitment, where many factors appear to be chemotactic
agents for eosinophils. For example, interleukin (IL)-5 is an
important factor in eosinophil recruitment, yet antibodies to
IL-5 failed to produce a clinically beneficial effect when
administered to patients with asthma.
The compounds described in this disclosure, if developed,
will enable the role of histamine H4 receptors in the process
of leukocyte recruitment to be tested in humans. Such trials
will determine the therapeutic potential of such compounds.
Use of a composition comprising a nicotine ligand and
an antidepressant - for treating ulcerative colitis
THE JOYCE CLARKE LIVING TRUST AGREEMENT (Clarke DE)
US-20050234024, 20 October 2005
A method for treating ulcerative colitis in a patient having
inflammatory bowel disease, emphysema, chronic heart
failure, lung cancer and esophageal cancer by administering
a composition comprising a combination of nicotine, its
analog or an antagonist, and an antidepressant is claimed. A
substitute for smoking comprising the composition and a kit
comprising the composition are also claimed. No suitable
advantage is given, and no suitable biological data are
presented. The antidepressant is claimed to be bupropion.
N
CH 3
N
US-20050234024
(Joyce Clarke Living Trust)
Current Opinion
Ulcerative colitis is a common inflammatory condition of the
colon that affects individuals of all ages in the developed
world. It has a major impact on the quality of life of those
affected and has an impact on the economy of developed
countries. Furthermore, ulcerative colitis is not well treated,
thus there is a need for an effective therapy, particularly one
that reduces the frequency of hospital admissions.
It is well documented that the incidence of ulcerative colitis
among non-smokers is 3- to 4-fold greater than among smokers
and that nicotine appears to be responsible for this protective
effect. In addition, when tobacco smokers cease smoking,
ulcerative colitis is often precipitated. While nicotine can be
used to treat ulcerative colitis, it is addictive and has many
actions on the cardiovascular system. Some laboratories have
investigated whether the mechanism of the addictive effect of
nicotine is distinct from the beneficial action with a view to
developing a selective agent, although none of these projects
has resulted in a clinically useful agent.
Bupropion is used when smokers are attempting to reduce
their dependence on nicotine (tobacco), although this drug is
not without adverse events. This disclosure describes an
interesting combination for the treatment of ulcerative
colitis, in which nicotine is used to treat colitis and
bupropion is used to prevent the depression that occurs on
withdrawal of the nicotine. Whether or not bupropion will
prevent nicotine addiction is unclear. Furthermore, it seems
unlikely that the addition of bupropion will prevent adverse
cardiovascular effects. Thus, much research is required to
see if this approach to the treatment of a disease with much
unmet medical need will have utility.
Cardiovascular & renal
Selected by Hermann AM Mucke (Pharmaceutical
Consultant and Analyst, Vienna, Austria) and Clifford
Whelan (Phlogopharm Ltd, Hatfield, Hertfordshire, UK)
New 4-hydroxycoumarin derivatives are vitamin K
epoxide reductase inhibitors - useful for the treatment of
coagulation disorders
ARYX THERAPEUTICS (Druzgala P, Becker C)
WO-2005100336, 27 October 2005
Novel 4-hydroxycoumarin derivatives, their salts and
compositions containing them are claimed. The compounds
are disclosed to be useful for the treatment of coagulation
disorders and to act by inhibiting vitamin K epoxide
reductase. The compounds are stable, and have a shorter
half-life and a lower incidence of side effects and toxicity
compared with prior art anticoagulants. The effect of several
compounds on vitamin K epoxide reductase activity was
determined. The specified compound displayed an IC50
value of 5.07 µM. The stability of the compounds to
metabolism by pooled human liver microsomes, containing
both CYP450 and esterase, with or without an NADPH cofactor,
was also determined. The specified compound had
stabilities at 90 min of 91 and 96%, respectively, and stability
in buffer of 92% at 90 min; both the compound and its
corresponding acid metabolite had no inhibitory effect on
human IKr in stably transfected HEK-293 cells, nor in a broad
cellular and biochemical receptor screening assay. The
specified compound, 1,1,1,3,3,3-hexafluoro-2-methylpropan-
2-yl 4-((4-hydroxy-2-oxo-2H-chromen-3-yl)methyl)benzoate,
is the only compound specifically claimed for use.

OH
O O
WO-2005100336
(Aryx)
C
H 3
Current Opinion
Vitamin K epoxide reductase recycles the epoxide created by
γ-glutamyl carboxylase before vitamin K can be re-used as an
essential cofactor for the post-translational γ-carboxylation of
several blood coagulation factors. Genetic polymorphisms of
this quite recently uncovered enzyme complex could be partly
responsible for the variable response to warfarin therapy, but
polymorphisms in the CYP2C9 gene, affecting S-warfarin
clearance, are probably more important. This has
spurred development of warfarin analogs (including
4-hydroxycoumarins) as more predictable anticoagulants. The
compounds of the invention contain a halogenated ester group,
which makes them more susceptible to degradation by
hydrolases, while reducing or eliminating their CYP450
metabolism. This should greatly alleviate the problem of drug
interaction, which is also typical for warfarin. Such designed
compounds could offer powerful alternatives to the current
platelet aggregation inhibitors.
Use of a composition to inhibit PUMA function in
cardiomyocytes - for preventing or reducing
ischemia/reperfusion-induced myocardial cell death
BOSTON BIOMEDICAL RESEARCH INSTITUTE (Erhardt P, Toth A)
WO-2005099772, 27 October 2005
The use of a composition to inhibit p53 upregulated modulator
of apoptosis (PUMA) function in cardiomyocytes is claimed for
preventing or reducing ischemia/reperfusion induced
myocardial cell death. The composition is administered during
or after an ischemic attack, and inhibits binding of PUMA to
Bcl-2 or Bcl-xL. It is claimed that the invention is also useful for
screening for inhibitors of PUMA expression, for preventing
cell death in stem-cell explants intended to restore cardiac
function. The invention provides an effective means of
protecting cardiomyocytes from cell death following
myocardial infarction. The hearts of PUMA-deficient mice
showed significantly better functional recovery at the end of
reperfusion than hearts from wild-type litter mates, including
recovery of left ventricular developed pressure, first derivatives
of left ventricular pressure, and left ventricular end-diastolic
pressure. In addition, the functional recovery of PUMAdeficient
hearts accompanies corresponding inhibition of
apoptosis and necrosis as well as reduced infarct size. Chemical
structures are provided in the source document.
Current Opinion
Following stroke or myocardial infarction, cells that are
deprived of a blood supply die. On reperfusion, many cells
that are at risk also die, often as a result of free radical
damage. Whereas cells killed as a direct result of the infarct
die from necrosis, those exposed to free radicals may
undergo apoptosis. Thus, an agent that inhibits apoptosis
may have utility in the acute therapy of ischemic disease.
The p53 gene modulates apoptosis and offers an attractive
O
O
F
F
F
F
F
F
Patent alert 9
target for the development of agents that modulate this
process.
This disclosure describes some experiments in which mice
deficient in the p53 upregulated modulator of apoptosis, a
factor that promotes apoptosis, developed smaller infarcts
and showed better recovery in a model of myocardial
infarction than their wild-type litter mates. Thus, in
principle, inhibition of apoptosis leads to a reduction in
infarct size and improved recovery. The disclosure claims
the use of antisense oligonucleotides as a means of inhibiting
apoptosis, although it is not clear how these agents would be
used therapeutically. Patients present clinically with an
infarct, thus any therapy with a long onset of action may not
have utility. Alternatively, the use of such compounds as
prophylactic agents in patients with a history of
cardiovascular disease may render these patients susceptible
to the development of tumors, given that many tumors do
not undergo apoptosis as a result of mutations in the p53
gene. Thus, while this disclosure is an interesting concept,
further research is required before the utility of the
hypothesis can be tested clinically.
Central & peripheral nervous system
Selected by Hermann AM Mucke (Pharmaceutical
Consultant and Analyst, Vienna, Austria)
Use of an annexin II inhibitor - for treating
neurodegenerative diseases or CNS disorders
QUARK BIOTECH INC/FUJISAWA PHARMACEUTICAL CO LTD
(Feinstein EM, Mett I, Shtutman M)
WO-2005091716, 06 October 2005
A method for treating neurodegenerative diseases, central
nervous system (CNS) disorders or injury to CNS, for example,
spinal cord injury and traumatic brain injury, comprising
administering a composition of an annexin II inhibitor is
claimed. The use of an annexin II inhibitor for promoting or
enhancing recovery from the claimed diseases and an inhibitor
of annexin II are also claimed. The neurodegenerative diseases
are claimed to be stroke, hypertension, cerebral vascular
disease, systemic hypotension, Parkinson's disease, epilepsy,
depression, amyotrophic lateral sclerosis, Alzheimer's disease,
Huntington's disease and HIV-induced dementia. A method for
diagnosing neurodegenerative diseases and ischemic events by
detecting the levels of annexin II polypeptide is disclosed. The
annexin II inhibitor is disclosed to inhibit neurotoxic-stressinduced
apoptosis. No suitable advantage is given, and no
suitable biological data are presented. The annexin II inhibitor is
claimed to be a compound, for example, sodium nitroprusside
or Tyrphostin AG1024, or an antisense polynucleotide.
Chemical sequences are provided in the source document.
C
H 3
C
H 3
HO
CH 3
Br
N
WO-2005091716
(Quark Biotech/Fujisawa)
N

10 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Current Opinion
The annexins are a family of highly homologous calcium
and phospholipid binding proteins. Annexin II serves as a
co-receptor for both plasminogen and tissue plasminogen
activator on endothelial cells and greatly facilitates the
generation of plasmin. Its primary role is believed to be in
coagulation, although involvement in cell-membrane fusion
and cancer invasion has also been demonstrated. This
invention relates to the discovery that the expression of
annexin II is involved in neuronal apoptosis induced by
oxidative or ischemic stress. Using stroke-specific neuronal
cDNA subtraction libraries on microarrays prepared from
rats before and after middle cerebral artery occlusion, the
inventors determined that the annexin II gene is upregulated
within 6 h of ischemia, reaches a maximum at 48 h and can
be repressed in vivo by pre-treatment with a specific siRNA.
In situ hybridization demonstrated induction of protein
expression on leukocytes and macrophages, but not in
neurons, which makes the invention less surprising because
this indicates that the neurotoxic action of annexin II is not a
direct one; rather it ties into known mechanisms. Only
detailed functional studies can reveal if this protein could
actually become a drug target or rather should be 'better left
alone' (Blood (2005) 105(5):1845-1846).
New ginkgolide derivatives and compositions are
amyloid β protein inhibitors - useful for the treatment of
Alzheimer's disease
THE TRUSTEES OF COLUMBIA UNIVERSITY IN THE CITY OF NEW
YORK (Vitolo OV, Nakanishi K, Shelanski ML, Krane S, Arancio
O, Jaracz S, Berova ND)
WO-2005092324, 06 October 2005
Novel ginkgolide derivatives, compositions containing
them, optionally in combination with an antioxidant,
compositions comprising a mixture of ginkgolides, a process
for the extraction of Ginkgo biloba, and the use of the
compositions for the treatment of neurological and
neurodegenerative disease, especially Alzheimer's disease,
are claimed. The composition produced by the claimed
process is stated to be more efficacious than the currently
available standardized extract Egb-761. Compounds were
tested as inhibitors of β-amyloid (1-42) protein-induced
long-term potentiation (LTP) in a hippocampal slice assay.
At concentrations of 1 µM, ginkgolide J and ginkgolide A
both restored long-term potentiation values to control levels,
while neither ginkgolide B nor ginkgolide C was effective.
Several compounds are specifically claimed for use, for
example, ginkgolide J. Compositions containing ginkgolide J
and ginkgolide A are also claimed.
O
O
H
CH 3
OH CH3 CH
OH 3
O
CH 3
O
O
OH O H
O
WO-2005092324
(Trustees of Columbia University)
Current Opinion
When extracts from Ginkgo biloba were first offered as
cognition enhancers several decades ago, their scientific
foundation was extremely narrow, and even a decade ago
our knowledge at the molecular level was limited. Today,
hardly a month passes in which the peer-reviewed and
patent literature does not carry new, well-founded
contributions concerning Ginkgo compounds. That
ginkgolide B can block β-amyloid (1-42)-induced
neurotoxicity had been published before, but scientists from
Columbia University have now extended this to ginkgolides
A and J. More importantly, they have shown that these
molecules also inhibit β-amyloid blockade of neuronal LTP.
At concentrations of 1 µM, ginkgolides A and J both restored
LTP in hippocampal slices to control levels, while the B- and
C-type molecules were ineffective. Less than a month before
the pertinent March 2004 priority date, a Ukrainian research
group had published the finding that 5 µM of ginkgolide B
(but not J) completely inhibited the induction of
hippocampal LTP (Neurochem Int (2004) 44(3):171-177). LTP
modulation has much more profound therapeutic
implications than simple neuroprotection, and in the case of
the ginkgolides it might be caused by the interplay of two
mechanisms: blockade of glycine binding sites and
antagonism of receptors for platelet-activating factor, a
bioactive lipid that has been proposed to be a retrograde
mediator of LTP.
Endocrine & metabolics
Selected by Peter Norman (Norman Consulting, Burnham,
Bucks, UK)
New sulfonamide derivatives are PPARα agonists -
useful for the treatment of, eg, lipid disorders and
atherosclerosis
PFIZER PRODUCTS INC (Hamanaka ES, Kehrli ME Jr)
WO-2005092845, 06 October 2005
Novel sulfonamide derivatives, their salts or prodrugs,
compositions containing them, optionally in combination
with additional active ingredients, and methods of their use for
the treatment of dyslipidemia, obesity, hypertriglyceridemia,
hyperlipidemia, hypoalphalipoproteinemia, metabolic
syndrome, diabetes mellitus, hyperinsulinemia, impaired
glucose tolerance, insulin resistance, diabetic complications,
atherosclerosis, hypertension, coronary heart disease,
hypercholesterolemia, inflammation, osteoporosis,
thrombosis, peripheral vascular disease, cognitive
dysfunction or congestive heart failure are claimed. These
compounds are stated to be peroxisome proliferatoractivated
receptor (PPAR) agonists, particularly PPARα
agonists. No suitable advantage is given. The ability of the
compounds to reduce postpartum serum non-esterified fatty
acid (NEFA) and liver triglyceride levels was determined in
calving dairy cattle following dosing (route unspecified) on
alternate days in the week prior to calving and for 8 days
following. Several compounds are specifically claimed, for
example, 2-methyl-5-(4'-trifluoromethoxybiphenyl-4-ylsulfamoyl)-benzoic
acid, which significantly (p < 0.01)

educed serum NEFA and liver triglyceride levels at a dose
of 0.5 mg/kg. Functional and anti-atherosclerotic studies are
additionally described, but no resulting data are presented.
F
F
F
O
H
N
S
O O
WO-2005092845
(Pfizer)
Current Opinion
PPAR agonists of varying specificities have attracted
considerable attention for the treatment of various metabolic
disorders. However, their development has encountered
many problems owing to side effects and toxicity, leading to
the abandonment of many compounds and causing the Food
and Drug Administration (FDA) to impose additional
toxicology requirements for this class of compounds. The
FDA's rejection of the dual PPAR agonist muraglitazar has
prompted Bristol-Myers Squibb Co and Merck & Co Inc to
consider discontinuing development of the drug. This
application is notable for two reasons: first, Pfizer has shown
limited interest in the development of PPAR agonists, and
second, because the acid head group in the claimed
compounds is present as a benzoic acid rather than the more
common phenylpropionic acid or its isosteres.
Use of alkyne MCH antagonists - for the treatment of,
eg, obesity, metabolic disorders or diabetes
BOEHRINGER INGELHEIM INTERNATIONAL GMBH (Stenkamp D,
Mueller SG, Lustenberger P, Lehmann-Lintz T, Roth GJ, Rudolf
K, Schindler M, Thomas L, Lotz R)
US-20050234101, 20 October 2005
The use of alkyne derivatives, their tautomers, enantiomers
or salts, or compositions comprising them, to influence
eating behavior, reduce body weight or prevent or treat a
metabolic disorder is claimed. The metabolic disorder is
claimed to be selected from the group consisting of bulimia,
bulimia nervosa, cachexia, anorexia, anorexia nervosa or
hyperphagia. The compounds are also claimed to be useful
for the treatment of diabetes, diabetic retinopathy,
neuropathy or nephropathy, insulin resistance, cardiac
insufficiency, arteriosclerosis, high blood pressure, arthritis,
hyperlipidemia, mastocytosis, emotional disorders, affective
disorders, depression, anxiety, sleep disorders, reproductive
disorders, sexual disorders, memory disorders, epilepsy,
dementia, hormonal disorders, urinary incontinence,
hyperactive urinary bladder, urgency or enuresis, and
dependencies or withdrawal symptoms. The compounds are
stated to act as melanin concentrating hormone (MCH)
antagonists. No specific advantage is given. The activity of
these compounds was assessed in an MCH-1 receptorbinding
test. Several compounds are specifically claimed, for
example, (2-{4-[5-(4-chlorophenyl)pyridin-2-ylethynyl]-2methylphenoxy}ethyl)(cyclohexyl)cyclopentylamine,
which
had an IC50 value of 6.2 nM.
O
OH
CH 3
N
O
C
H 3
US-20050234101
(Boehringer Ingelheim)
N
Patent alert 11
Current Opinion
Obesity is a major problem in all developed countries and is
an underlying causal factor in the development of many
other conditions, such as type 2 diabetes and heart disease.
Despite this, there are few approved therapeutic agents for
the treatment of obesity, and none of the currently marketed
drugs are well tolerated. A number of new approaches for
the treatment of obesity are under investigation and the
development of MCH antagonists is prominent in this
regard. Boehringer has not previously shown an interest in
this target; however, this application and WO-2005085221
suggest that this is another research area in which the
company is actively involved, and that it is seeking to
expand its metabolic disease portfolio.
New substituted pyrimidine derivatives are DPP-IV
inhibitors - useful for treating, eg, diabetes, cancer,
autoimmune disease, HIV infection and immunodeficiency
SYRRX INC (Feng J, Gwaltney SL, Stafford JA, Zhang Z)
WO-2005095381, 13 October 2005
Novel substituted pyrimidine and related derivatives, a
process for their preparation and methods of their use for
inhibiting dipeptidyl peptidase (DPP)-IV and for the
treatment of types 1 and 2 diabetes, cancer (particularly
colorectal, prostate, breast, thyroid, skin, lung or head and
neck cancer), autoimmune disorders (including rheumatoid
arthritis, psoriasis and multiple sclerosis), HIV infection,
inadequate lymphocyte or hematopoietic cell levels,
chemotherapy or radiation therapy side effects (particularly
kidney failure and bone marrow disorders) and
immunodeficiency are claimed. The compounds are
selective for DPP-IV over other proteases. Protocols for
protease inhibition assays are described. The compounds are
stated to exhibit selective DPP-IV inhibitory activity at
concentrations of at least 50-fold less than those required to
inhibit fibroblast activation protein-α, with Ki values
ranging between 10 -9 and 10 -5 M, but no specific data are
presented. Several compounds are specifically claimed,
including 2-(6-[3(R)-aminopiperidin-1-yl]-3-methyl-2,4-dioxo-
3,4-dihydro-2H-pyrimidin-1-ylmethyl)benzonitrile.
N
H 2
N
N
N
O
N
WO-2005095381
(Syrrx)
O
CH 3
Cl

12 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Current Opinion
A number of new approaches to the treatment of diabetes
are being pursued. Of these, the development of DPP-IV
inhibitors is by far the most advanced, with three
compounds (MK-431 (Merck & Co Inc/Banyu
Pharmaceutical Co Ltd/Ono Pharmaceutical Co Ltd),
saxagliptin (Bristol-Myers Squibb Co) and vildagliptin
(Novartis Institutes for BioMedical Research Inc)) currently
in phase III clinical trials. These compounds, like nearly all
other DPP-IV inhibitors, are based on the almost ubiquitous
2-pyrrolonitrile chemotype. Few other chemotypes have
been described, and the compounds claimed in this
application represent a considerable variation in this regard.
This difference may be due to the successful exploitation of
structure-aided drug design that is the focus of research at
Takeda San Diego (formerly Syrrx).
Oncological
Selected by Peter Norman (Norman Consulting, Burnham,
Bucks, UK)
New 6-phenylfuro[2,3-d]pyrimidine derivatives are DDR2
tyrosine kinase inhibitors - useful for the treatment of
rheumatoid arthritis, cirrhosis and cancer
KOREA INSTITUTE OF SCIENCE AND TECHNOLOGY/JEIL
PHARMACEUTICAL CO LTD (Yang B-S, Yang K-M, Kim H-J, Park
I-S, Park S-D, Lee J-H, Kwon H-M, Woo B-Y)
WO-2005092896, 06 October 2005
Novel 6-phenylfuro[2,3-d]pyrimidine derivatives and their
salts, compositions containing them, their use as inhibitors
of the discoidin domain receptor (DDR)2 tyrosine kinase,
and in the treatment of hepatocirrhosis, rheumatism and
cancer are claimed. The DDR protein has been reported to
enhance the development of fibroblasts and to show
increased expression in metastatic cancer cells. The claimed
compounds are the first low-molecular-weight inhibitors of
DDR2 kinase described. In a rat cannulated bile duct model
of cirrhosis, administration of one compound (10
mg/kg/day for 2 weeks) inhibited hydroxy furorin
production from 4.93 to 2.23 mg/g (the normal level).
Approximately 200 compounds are exemplified. No
compounds are specifically claimed.
Cl
O
N
CH3 HN
WO-2005092896
(Korea Institute of Science and Technology/Jeil)
Current Opinion
DDR2 is a widely expressed member of a subfamily of
receptor tyrosine kinases whose ligands are fibrillar
collagens. Studies in knockout mice suggest that it acts to
regulate cellular proliferation and, for example, fibroblast
signaling. Tyrosine kinases in this subfamily have attracted
little attention until now, thus the appearance of this
application claiming the first documented inhibitors of
N
S
N
N
DDR2 kinase is likely to evoke considerable efforts in the
field. The claimed compounds also represent a novel
chemotype of tyrosine kinase inhibitor, which may have
enhanced selectivity compared with the better characterized
tyrosine kinases.
New thioalkeneamide derivatives are transketolase
inhibitors - useful for the treatment of cancer
ARRAY BIOPHARMA INC (Boyd SA)
WO-2005095344, 13 October 2005
Novel thioalkeneamide derivatives and their use, either
alone or in combination with a thiamine-restricted diet
and/or other therapeutic agents, to inhibit transketolase
activity and cellular nucleic acid synthesis, and to reduce the
cellular levels of ribulose/ribose-5-phosphate are claimed.
These compounds are also claimed to increase apoptosis in
tumor cells and to reduce tumor growth. They are stated to
be additionally useful as inhibitors of metastasis and
angiogenesis. No suitable advantage is given. Several
compounds are specifically claimed, including N-(2-amino-6methylpyridin-3-ylmethyl)-N-{2-[2-[(2-amino-6-methylpyridin-3ylmethyl)formylamino]-1-(2-hydroxyethyl)-propenyl-disulfanyl]-
4-hydroxy-1-methylbut-1-enyl}formamide (AR-00342632), which
had an IC50 value of 10 nM against HCT116 colon carcinoma
cells in vitro.
C
H 3
N
NH 2
C
H 3
N
O
H
S S
OH
OH
H
WO-2005095344
(Array)
N
CH 3
O NH 2
Current Opinion
Transketolase is a metabolic enzyme that plays a crucial role
in tumor cell nucleic acid synthesis, using glucose through
the elevated non-oxidative pentose phosphate pathway.
Thus, inhibitors of this enzyme constitute a novel approach
to the treatment of cancer. To date, this possibility has been
almost completely neglected, with only Array's disclosure of
the activity of AR-00342632 at the 2005 American Chemical
Society meeting, and S*BIO and Chiron's description of the
identification of lead compounds via high-throughput
screening indicating any interest. This application was one
of two from Array (see also WO-2005095391). AVEO
Pharmaceuticals published WO-2005094803 claiming such
inhibitors on the same day.
New 2-aminomethylthiazole-5-carboxamide derivatives
are protein kinase modulators - useful for the treatment
of, eg, neurological disease and cancer
LEXICON GENETICS INC (Jin H, Shi Z-C, Theis H, Kolb H)
WO-2005097766, 20 October 2005
New 2-aminomethylthiazole-5-carboxamide derivatives,
their compositions, and their use for the treatment of, for
example, allergy, cardiovascular disease, cancer, dental
disease, dermatological disease, endocrine disease,
metabolic disorder, gastrointestinal disease, genitourinary
N
CH 3

disease, hematological disease, hepatobiliary disease,
infection, musculoskeletal disease, neurological disease,
nutritional disorder, ocular disease, psychiatric disorder,
pulmonary disease and leukemia are claimed. It is disclosed
that the compounds can be used for the treatment of
diseases mediated by protein kinase inhibition. No suitable
advantage is given. No biological data are presented. The
specified compound is one of several 2-aminomethylthiazole-5-carboxamide
compounds specifically claimed.
C
H 3
N
N
S
N
N
H
O
WO-2005097766
(Lexicon Genetics)
CH 3
O CH3
Current Opinion
Lexicon Genetics is one of several genomics companies that
has switched its business strategy to pursue the
development of small-molecule therapeutics. In January
2005, Lexicon Genetics indicated that it had identified two
small-molecule candidates, the more advanced of which
(LX-1521) is an anti-apoptotic kinase inhibitor discovered
from Lexicon's LG152 kinase target program. Until October
2005, Lexicon Genetics had not published any patent
applications claiming kinase inhibitors. The appearance of
this application and WO-2005095420, which claims
thiazolopyrazoles, provides the first indication as to the
chemical strategy that is being pursued.
New 3-aminopyrazole derivatives are tropomyosinrelated
kinase inhibitors - useful for the treatment of
cancer and fibroproliferative/differentiative disorders
ASTRAZENECA AB/ASTRAZENECA UK LTD (Lyne P, Wang B,
Wang T)
WO-2005103010, 03 November 2005
Novel 3-aminopyrazole derivatives, their salts, processes for
their preparation, compositions containing them and
methods of their use as tropomyosin-related kinase (Trk)
inhibitors for the treatment of cancers, fibroproliferative/
differentiative disorders, psoriasis, rheumatoid arthritis,
Patent alert 13
Kaposi's sarcoma, hemangioma, nephropathy, atheroma,
atherosclerosis, arterial restenosis, autoimmune disease,
inflammation, bone disease or ocular disease with retinal
vessel proliferation are claimed. The compounds are
particularly stated to inhibit TrkA and TrkB activity. No
suitable advantage is given. The ability of compounds to
inhibit TrkA and TrkB activity was determined in vitro using
an amplified luminescent proximity assay and appropriate
biotinylated polypeptide substrates. Compounds are stated
to have IC50 values of 0.01 to 10 µM against TrkB activity. No
specific biological data against TrkB are presented. Six
compounds are specifically claimed, for example, (R)-4-(5cyclopropyl-1H-pyrazol-3-ylamino)-2-[1-(4-fluorophenyl)-
2-hydroxyethylamino]-5-nitrobenzonitrile, which had an
IC50 value of 0.859 µM against TrkA.
F
HO
N
H
N
H
N
N
WO-2005103010
(AstraZeneca)
Current Opinion
TrkA and TrkB are two members of the Trk proto-oncogene
family and thus constitute logical targets for the
development of novel anticancer agents. Despite this,
relatively few small-molecule inhibitors of these kinases
have been described to date, and, of those that have, a
number are broad-spectrum kinase inhibitors. AstraZeneca
is the first company to describe compounds that appear to
be specific inhibitors of these kinases, and which also
represent a fairly novel kinase inhibitor chemotype. This
application claims compounds similar to those
claimed in the application WO-2005049033, but employs
pyrazolyl-aminobenzene derivatives rather than pyrazolylaminopyrimidines.
NH
N +
O
O

14
Editorial overview
The genome: Five years on
Michael Williams
Address
Department of Molecular Pharmacology and Biological Chemistry
Feinberg School of Medicine
Northwestern University
Chicago
IL 60611
USA
Email: mazarine1643@comcast.net
Current Opinion in Investigational Drugs 2006 7(1):14-17
© The Thomson Corporation ISSN 1472-4472
In 2001, one of the major milestones in the history of
biomedical research was achieved, namely the publication of
draft maps of the human genome [1,2], an activity that was
reportedly completed in 2003 [3]. This was inevitably
accompanied by various predictions that the discrete
molecular source of all human diseases would soon be
known [4-6] and, as a consequence, that the path to the
discovery of novel, more efficacious and safer drugs, based
on as yet unknown and unproven targets resident in the
genome, would be exponentially more facile, more
productive, faster and cheaper, owing to the unique diseaseassociation
of the targets. The then US President, Bill
Clinton, predicted that 'with this new found knowledge,
humankind is on the verge of gaining immense new power
to heal' [7]. Conversely, recent research by Accenture/CMR
International notes that 'only 3% of projects aimed at new
targets will enter preclinical development compared with
17% for projects on established targets' [8].
Almost five years later, an informal survey of 500 scientists
involved in the drug discovery process found that 67% were
unconvinced that the genome maps had 'even moderate
effects on drug research' [9]. Similarly, biotechnology
industry observers and genomic scientists cautioned that the
promised 'fruits of genomics' [10] are unlikely to emerge in
the near future, with a 10 to 20 year timeframe being
considered more likely [11].
Additionally, in following the theme of using novel
approaches to finding new drugs, in this same group of 500
scientists, 64% 'considered that their organization, at best,
only supported innovation to a moderate extent' [9], echoing
similar comments made by Drews [12] and Vagelos [13].
This finding indicated a disconnect between the concept of
innovation−'the act of introducing something new'−that is
religiously cited as the driver for drug discovery [8,14], and
the rampant technology acquisition and implementation in
the biotech and pharmaceutical industries over the past
decade. Clearly, the acquisition of enabling technologies is
very distinct from their effective use and subsequent ability
to impact the way things are done. In reflecting on the
contributions of the late Paul Janssen to the pharmaceutical
industry, Black noted that successful drug discovery should
avoid 'wishful thinking' and superficiality, and focus instead
on conception, concentration, commitment and creativity
[15]. In this context, the strategic management of the
drug-discovery process appears critical to support the
process of innovation and entrepreneurship [16] to ensure
that the enabling technologies actually contribute to, rather
than diffuse, the focus.
As with many of the new technologies in biomedical
research, the expectations for genome-based information
have far outweighed their fledgling status with 'overhyping'
being a frequently expressed concern [17-20]. Genetics was
described as a 'science of exceptions' by Jones in 2000, with
human life expectancy far more dependent on the
environment (epigenetics) than the genome (genetics) [17].
Jones also noted that geneticists have made promises
regarding the deliverables in genetics for decades,
controversially suggesting that four letters of the genetic
code might more reasonably be H, Y, P and E.
However, hype related to new technology introductions is not
unique to either the genome or biomedical research and has
been formalized in Fenn's 'hype cycle' (Figure 1) [21]. Initially
used in 1995, the concept has been more broadly extended to
the maturity and adoption rates of a wide range of emerging
technologies in different industries. The question for the
genome-based, biomedical research enterprise in 2006 is where
genome-based drug discovery currently lies on the maturity
scale. One may argue that the thought leaders in genomics are
still operating in the 'peak of inflated expectations', while those
reducing the genome to practice (by fiat or choice) in pharma
and biotech are operating in the 'trough of disillusionment'
(Figure 1) [9]. The sceptics are at least ahead of the pundits on
the hype cycle abscissa of maturity.
While many heritable disorders have already been identified in
which a mutation in a single gene is necessary and sufficient to
produce a disease, critics of genome-based drug discovery have
pointed out that the genetic associations for Huntington's
disease [22], sickle cell anemia [23] and cystic fibrosis [24] were
known before the mapping of the genome and, despite the
identification of discrete molecular lesions involving these
associations, have yet to yield effective treatments. Similarly, in
the Alzheimer's disease (AD) field, the two key mechanisms
thought to contribute to disease progression and neuronal
death−amyloid β deposition and tau hyperphosphorylation
[25]−together with the genetic association of AD with
apolipoprotein E alleles [26], have been active research targets
for many years with, again, little progress having been made in
either understanding the origin and contribution of the
molecular lesion to disease etiology or how this knowledge can
be used to find effective treatments. Of additional concern in
the area of AD therapeutics is that the National Institute for
Health and Clinical Excellence in the UK has recently
recommended that the drugs currently approved for use in the
treatment of AD (eg, donezepil) are no longer prescribed,
because their benefit to the patient does not justify their cost
[27]; the implications of this recommendation represent part of
a much broader debate [28].

Figure 1. The hype cycle.
Visibility
Technology
trigger
Positive
hype
Don't join in just because it's 'in'
Peak of inflated
expectations
Negative
hype
Don't miss out just because it's 'out'
Trough of
disillusionment
Maturity
Slope of
enlightenment
Plateau of
productivity
Editorial overview 15
Technology trigger: a breakthrough technology that generates significant interest and rampant acquisition and deal making and claims to
revolutionize the future of drug discovery.
Peak of inflated expectations: a phase of over enthusiasm and unrealistic predictions in the press, during which successes in terms of
investigational new drugs are infrequent. Conference organizers reap the benefits from organizing frequent 'updates' on the usefulness and
utilization of the technology with speakers who spend the majority of their time attending such conferences and are thus removed from the
practicalities of trying to use the technology effectively.
Trough of disillusionment: the technology sinks from the limelight as it did not live up to its over-inflated expectations; technocrats and
research management move onto the next technology trigger in the hope that this will be 'the one'. The phenomenon of hype addiction is
apparent.
Slope of enlightenment: additional focused research leads to a true understanding of the utility of the technology (eg, parallel synthesis
versus combinatorial chemistry).
Plateau of productivity: the practical benefits of the technology are widely demonstrated and accepted. It is found to make a big difference
just as those who are long gone said they thought it would (modified from reference [45]).
(Reproduced with permission from Gartner and Linden A, Fenn J: Understanding Gartner's Hype Cycles. Research ID R-20-197, Gartner,
Stamford, CT, USA. © 2003 Gartner) [21].
Additional examples of tantalizing gene associations with
disease phenotypes that have already been established, yet
remain controversial, are: the dopamine transporter and
attention-deficit hyperactivity disorder [29], the breast
cancer gene and cancer [30], the cystic fibrosis
transmembrane conductance regulator and cystic fibrosis
[31], and α1 antitrypsin deficiency and chronic obstructive
pulmonary disease [32].
An interesting observation regarding the perceived
commercial value of the genome, albeit an extremely shortterm
view, is that the majority of the high-profile
genomic/genetics companies founded in the 1990s
[33]−Celera, Human Genome Sciences, Incyte, Millennium,
Exelexis, Curagen and Genset−have either dramatically
changed their business model toward that of more
traditional biotechs (eg, small-molecule and/or biologicals
drug discovery) or ceased to exist, leaving only Myriad
Genetics in Salt Lake City, USA and DeCode genetics, based
primarily in Reykjavik, Iceland, as the remaining two
players of note in the field of genome-based medicine, each
building on unique access to discrete patient populations
with extensive genealogical and genetic records: members of
the Mormon Church in Salt Lake City, and the population of
Iceland in Reykjavik.
With an increasing recognition of the significant challenges
inherent in translating genomic information to practice (the
99% perspiration part of the definition of genius ascribed to
Thomas Edison), thought leaders have had no compunction
in leaving the incomplete business of the genome behind to
focus their attentions on the many other 'omics' that exist
beyond the genome. These include proteomics [34], which
provides even bigger technical challenge than genomics,
given an infinitely more complex data set full of labile
unknowns dependent on post-translational modification
(such as phosphorylation, glycosylation and splicing) and
the need for extensive subproteomic analysis based on the
current limitations of mass spectrometroscopic-based
analytical capabilities that lag far behind the questions being
posed [35,36].
The latest of the 'omic' sciences is that of the 'interactome'
[37], an evolving collection of binary protein-protein

16 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
interactions that may form the scaffold for functional genomics
and proteomics, that has emerged from the recently published
draft of the human haplotype map (HapMap) [37,38]. HapMap
is anticipated to 'provide insight into development and disease
mechanisms at a systems level' and to facilitate genome-wide
association studies, representing a major step forward in
understanding human disease etiology, provided that the same
concerns regarding data replication that are prevalent in the
genome [39], and more so in the proteome [36], are not a
function of the enhanced complexity and practice of the
interactome [40].
While there is early enthusiasm for the promise of the
interactome (the 'technology trigger' phase of the hype cycle)
Sharon Begley of the Wall Street Journal (who brought the
world the parts model of the Boeing 777 as a metaphor for
the reductionistic approach to deciphering the genome) [41]
has questioned the 'limited' value of the HapMap [19] in the
context of twin studies [42] in which identical DNA and
haplotypes lead to different phenotypes.
During the course of this year, Current Opinion in
Investigational Drugs hopes to present a series of Editorials,
written or suggested by members of its Editorial Board, that
are focused on the challenges and progress in utilizing
information from the genome and its 'omic' progeny in the
context of both discrete therapeutic areas and genomeassociated
technology platforms. In an era of considerable
scepticism as to the value of new biologies [9,18] and their
ability to be integrated with more traditional approaches to
drug discovery [43], the capacity of these disciplines to add
to the solutions, rather than the problems that are deemed to
be contributing to the dearth of new drug introductions [8,
43,44], will be reviewed.
Suggested reading
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Devon K, Dewar K, Doyle M, Fitz Hugh W, Funke R et al: Initial
sequencing and analysis of the human genome. Nature (2001)
409(6822):860-921.
2. Venter JC, Adams MD, Myers EW, Li PW, Mural RJ, Sutton GG, Smith
HO, Yandell M, Evans CA, Holt RA, Gocayne JD et al: The sequence
of the human genome. Science (2001) 291(5507):1304-1351.
3. Collins FS, Morgan M, Patrinos A: The human genome project:
Lessons from large-scale biology. Science (2003) 300(5617):286-
290.
4. Moore SD: Biotechnology executives discuss the impact of the
genetic revolution. Wall Street Journal (2000) July 24:B10-B11.
5. Collins FS, Green ED, Guttmacher AE, Guyer MS: A vision for the
future of genomics research. Nature (2003) 422(6934):835-847.
6. Stoughton RB, Friend SH: How molecular profiling could
revolutionize drug discovery. Nat Rev Drug Discov (2005) 4(4):345-
350.
7. Belkin L: A doctor for the future. New York Times Magazine (2005)
November 06:68-115.
8. Carney S: How can we avoid the productivity gap? Drug Disc Today
(2005) 10(15):1011-1013.
9. Carney S: Question: What do you call 500 scientists coming
together to address the productivity gap? Answer: A start. Drug
Disc Today (2005) 10(15):1025-1029.
10. Lehman Brothers/McKinsey & Co: The Fruits of Genomics. New York,
NY, USA (2001) January.
11. Weatherall D: Personalised medicines: Hopes and realities. Royal
Society, London, UK (2005):1-52.
12. Drews J: Strategic trends in the drug industry. Drug Disc Today
(2003) 8(9):411-420.
13. Osbourne E: After plateau, 'big growth phase' due for
biotechnology: Vagelos. BioWorld Today (2005): May 25.
14. Frantz S: Europe fiddles while innovation burns. Nat Rev Drug
Discov (2005) 4(9):704-705.
15. Black J: A personal perspective on Dr Paul Janssen. J Med Chem
(2005) 48(6):1687-1688.
16. Sams-Dodd F: Optimizing the discovery organization for
innovation. Drug Disc Today (2005) 10(15):1049-1056.
17. Jones S: Genetics in Medicine: Real Promises, Unreal
Expectations. Milbank Memorial Fund Report (2000) 9:June.
18. Kubinyi H: Drug research: Myths, hype and reality. Nat Rev Drug
Discov (2003) 2(8):665-668.
19. Guttmacher AE, Collins FS: Realizing the promise of genomics in
biomedical research. J Am Med Assoc (2005) 294(11):1399-1402.
20. Begley S: Linking DNA profiles to diseases may not lead to
prevention. Wall Street Journal (2005) November 04:B1.
21. Linden A, Fenn J: Understanding Gartner's hype cycles. Research ID
R-20-197, Gartner, Stamford, CT, USA (2003).
22. Marx J: Neurodegeneration: Huntington's research points to
possible new therapies. Science (2005) 310(5745):43-45.
23. Edwards CL, Scales MT, Loughlin C, Bennett GG, Harris-Peterson S,
De Castro LM, Whitworth E, Abrams M, Feliu M, Johnson S, Wood M et
al: A brief review of the pathophysiology, associated pain, and
psychosocial issues in sickle cell disease. Int J Behav Med (2005)
12(3):171-179.
24. Rubenstein RC: Novel, mechanism-based therapies for cystic
fibrosis. Curr Opin Pediatr (2005) 17(3):385-392.
25. Forman MS, Trojanowski JQ, Lee VM-Y: Neurodegenerative
diseases: A decade of discoveries paves the way for therapeutic
breakthroughs. Nat Med (2004) 10(10):1055-1063.
26. Fenili D, McLaurin J: Cholesterol and ApoE: A target for Alzheimer's
disease therapeutics. Curr Drug Targets CNS Neurol Disord (2005)
4(5):553-567.
27. Whalen J: Britain stirs outcry by weighing benefits of drugs versus
price. Wall Street Journal (2005) November 27:A1-A11.
28. Avorn J: Powerful Medicines: The Benefits, Risks and Costs of
Prescription Drugs. Knopf, New York, NY, USA (2004):1-464.
29. Langley K, Turic D, Peirce TR, Mills S, Van Den Bree MB, Owen MJ,
O'Donovan MC, Thapar A: No support for association between the
dopamine transporter (DAT1) gene and ADHD. Am J Med Genetics
Part B: Neuropsychiatric Genetics (2005) 139(1):7-10.
30. Couzin J: Choices−and uncertainties−for women with BRCA
mutations. Science (2003) 302(5645):592.
31. Des Georges M, Guittard C, Altieri J-P, Templin C, Sarles J, Sarda P,
Claustres M: High heterogeneity of CFTR mutations and unexpected
low incidence of cystic fibrosis in Mediterranean France. J Cystic
Fibrosis (2004) 3(4):265-272.
32. DeMeo DL, Silverman EK: Genetics of chronic obstructive pulmonary
disease. Semin Respir Crit Care Med (2003) 24(2):151-160.
33. Rabinow P: French DNA. University of Chicago Press, Chicago, IL,
USA (1999).
34. Figuys D: Proteomics: The basic overview. In: Industrial Proteomics:
Applications for Biotechnology and Pharmaceuticals. John Wiley & Sons
Inc, New York, NY, USA (2005):1-62.

35. Huber LA: Is proteomics heading in the wrong direction? Nat Rev
Mol Cell Biol (2003) 4(1):74-80.
36. Kopec K, Bozyczko-Coyne D, Williams M: Target identification and
validation in drug discovery: The role of proteomics. Biochem
Pharmacol (2005) 69(8):1133-1139.
37. Rual J-F, Venkatesan K, Hao T, Hirozane-Kishikawa T, Dricot A, Li N,
Berriz GF, Gibbons FD, Dreze M, Ayivi-Guedehoussou N, Klitgord M et
al: Towards a proteome-scale map of the human protein-protein
interaction network. Nature (2005) 437(7062):1173-1178.
38. Altshuler D, Brooks LD, Chakravarti A, Collins FS, Daly MJ, Donnelly P,
International HapMap Consortium: A haplotype map of the human
genome. Nature (2005) 437(7063):1299-1320.
39. Williams M: Genome-based drug discovery: Prioritizing disease
susceptibility/disease-associated genes as novel drug targets for
schizophrenia. Curr Opin Investig Drugs (2003) 4(1):31-36.
Editorial overview 17
40. Kruglyak L: Power tools for human genetics. Nat Genet (2005)
37(12):1299-1300.
41. Begley S: Biologists hail dawn of a new approach: Don't shoot the
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www.wordspy.com/words/hypecycle.asp

18
Editorial overview
Steroid therapy for exudative age-related macular degeneration: Bridging
the gap until a cure is found
Maneli Mozaffarieh & Andreas Wedrich*
Address
Department of Ophthalmology
Medical University of Graz
Auenbruggerplatz 4
A-8036 Graz
Austria
Email: andreas.wedrich@meduni-graz.at
* To whom correspondence should be addressed
Current Opinion in Investigational Drugs 2006 7(1):18-19
© The Thomson Corporation ISSN 1472-4472
Age-related macular degeneration (AMD) is a devastating
disease affecting individuals of over 50 years of age, and is
the leading cause of irreversible blindness in the developed
world [1,2]. It is estimated that 1.6% of the population in the
50- to 65-year-old age group is affected, and in the UK there
are 16,000 new cases per year. The implications of this
untreatable disease in terms of social impact, healthcare
costs and personal misery are considerable. Current
treatments for both the wet and dry forms of the disease are
of limited efficacy [3], and, therefore, there is keen interest
among scientists and physicians to develop new therapies.
Corticosteroids have long been the cornerstone of ocular
anti-inflammatory therapy. In addition, they can suppress
cell proliferation. Consequently, steroids have been used for
the treatment of several ocular diseases, administered either
locally or systemically. In recent years, one particular
steroid, triamcinolone acetonide, has received much
attention from scientists. Various researchers studied the
possibility of injecting this corticosteroid directly into the
eye, firstly in animals [4,5] and later in selected patients. The
intravitreal use of this corticosteroid gained popularity
amongst ophthalmologists for the treatment of a wide range
of retinal diseases, including diabetic and cystoid macular
edema and exudative AMD.
Steroids, along with the majority of other drugs, do not exert
solely beneficial effects. One common side effect is the rise of
intraocular pressure (IOP) that is associated with steroid use.
This issue was addressed in a study where a group of
known steroid responders were treated with four different
steroids topically [6]. The results of this study showed that
IOP did not begin to increase until after 3 and 5 weeks of
treatment. The beauty of this finding for ophthalmologists
was that in the worst-case scenario, there remains a 3-week
window of relative safety when treating with a topical
ophthalmic corticosteroid. Moreover, almost all patients
with primary-care conditions respond to treatment in less
than 2 weeks when the steroid is applied topically.
Therefore, should we be concerned about the risk of IOP
elevation after triamcinolone acetonide intravitreal use for
exudative AMD? Furthermore, do we increase the chances
of improved vision for patients in the long term when
injecting this steroid through the intravitreal route? The
results of some of the research that has been conducted in
this area show that even 4 mg of intravitreal triamcinolone
significantly raises IOP [7,8]. In one particular study, the
researchers describe using 25 mg of triamcinolone for
intravitreal injections [9], which may increase IOP even more
significantly. The investigators suggested that the advantage of
a higher dose would be the longer intraocular availability of the
drug [10], rather than the temporary visual improvements
encountered in patients after intravitreal injections [8], despite
the possible side effects. It appears that our scientific
enthusiasm for possible visual improvements in exudative
AMD with steroid injections has forced us to step sideways.
Indeed, various studies suggest that in exudative AMD, the
modes of action of triamcinolone are linked to the
downregulation of inflammatory markers and endothelial
cell permeability [11,12]. However, moderate-to-high
concentrations of this drug would be required at the site of
action in order to prevent further growth of subretinal
neovascular tissue. For patients, this requirement would mean
that triamcinolone must be injected repeatedly, otherwise visual
improvements would only occur in the short term [8]. The
question that then arises is up to how many intravitreal
injections of this steroid can be tolerated by the eye of each
patient? Unfortunately, most of the research that has been
conducted in this area to date has not been associated with a
long enough follow-up time, one of the longer follow-up times
being 18 months [7]. We therefore do not have a fair idea of the
actual long-term outcome (ie, visual improvement or the side
effects of this drug), particularly when injecting via the
intravitreal route more than once.
Another concern when using intravitreal steroids is the
association of steroid use with an increase in lens opacity. In
one particular study in which intravitreal injections of
triamcinolone were administered for the treatment of diffuse
diabetic macular edema [13], a 3-fold increase of the posterior
subcapsular cataract score among phakic patients occurred.
This trend toward cataract progression suggests that cataract is
a likely risk of steroid injections. Cataracts influence quality-oflife
measures [14], and therefore a delay of cataract onset could
have a tremendous influence on the health of patients and on
healthcare costs. The issue of cataract progression is also of
particular interest for patients with AMD, because there is
controversy regarding the possible benefits or risks of cataract
surgery in these patients. While some reports suggest that
cataract surgery may worsen the progression of AMD [15,16],
others describe a benefit [17,18]. It may therefore be more
justified to resist the temptation to treat patients with multiple
intravitreal steroid injections as there is currently no evidence
of long-term benefits and, by increasing the chances of
cataracts, patients may become more vulnerable to possible
side effects after surgery.
A further side effect of corticosteroid injections is steroidinduced
infection [19,20]. Some researchers have reported

cases of pseudo-endophthalmitis [21], which appear to
resolve without any specific treatment. At this point we can
only postulate that, in case of true infectious
endophthalmitis, the course of the disease may be altered in
the presence of a moderate-to-high dose (25 mg) of
triamcinolone acetonide, which may necessitate patients
being treated aggressively. Placebo-controlled clinical trials
in large multicenter populations, with a long-term followup,
could provide evidence of the efficacy of this drug and
assess possible side effects and complications. However, it
may be difficult to design effective placebo-controlled trials
in a study for which an invasive procedure is required.
Overall, there is still no strong body of scientific evidence to
support the benefits of intravitreal injections of steroids in
the prevention of age-related eye disease. Additional data
regarding the toxic effects of steroids on the retina and optic
nerve, the optimum dosage and the number of intravitreal
injections that can be tolerated by the eyes of the patients, as
well as the perceptions of the patients themselves and
quality-of-life measures, could provide physicians with
more insight and help them to understand the long-term
risks and benefits for patients.
So why should we proceed with caution in view of the
possibility that intravitreal injections of steroids may have
important benefits? Firstly, making recommendations before
there is adequate knowledge to support long-term effects
erodes the credibility of science in the eyes of the public.
Moreover, intravitreal triamcinolone acetonide injections
may not promote additional gain in the quality of life or
overall health of the patients. We suggest that physicians
effectively educate their patients with regard to all benefits
and possible side effects of steroids in order for the patients
to establish realistic expectations. In particular, they should
be informed that there is no firm scientific knowledge as to
whether steroid injections are at all beneficial in the longterm
for the treatment of exudative AMD. Further careful
investigations of the pathogenesis of AMD, in addition to
studies of the effects of intravitreal steroid injections, are
required in order to gain a greater understanding of the
treatment possibilities for this debilitating disease. Until
then, intravitreal steroid injections will remain a bridge over
the therapy gap until a cure is found.
Suggested reading
1. Bressler NM, Bressler SB, Fine SL: Age-related macular
degeneration. Surv Ophthalmol (1988) 32(6):375-413.
2. Klein R, Klein BE, Linton KL: Prevalence of age-related maculopathy.
The Beaver Dam Eye Study. Ophthalmology (1992) 99(6):933-943.
3. Mozaffarieh M, Sacu S, Wedrich A: The role of the carotenoids, lutein
and zeaxanthin, in protecting against age-related macular
degeneration: A review based on controversial evidence. Nutr J
(2003) 2:20.
4. Ciulla TA, Criswell MH, Danis RP, Hill TE: Intravitreal triamcinolone
acetonide inhibits choroidal neovascularization in a laser-treated
rat model. Arch Ophthalmol (2001) 119(3):399-404.
Editorial overview 19
5. Danis RP, Bingaman DP, Yang Y, Ladd B: Inhibition of preretinal and
optic nerve head neovascularization in pigs by intravitreal
triamcinolone acetonide. Ophthalmology (1996) 103(12):2099-2104.
6. Leibowitz HM, Bartlett JD, Rich R, McQuirter H, Stewart R, Assil K:
Intraocular pressure-raising potential of 1.0% rimexolone in
patients responding to corticosteroids. Arch Ophthalmol (1996)
114(8):933-937.
7. Challa JK, Gillies MC, Penfold PL, Gyory JF, Hunyor AB, Billson FA:
Exudative macular degeneration and intravitreal triamcinolone: 18
month follow up. Aust N Z J Ophthalmol (1998) 26(4):277-281.
8. Danis RP, Ciulla TA, Pratt LM, Anliker W: Intravitreal triamcinolone
acetonide in exudative age-related macular degeneration. Retina
(2000) 20(3):244-250.
9. Jonas JB, Kreissig I, Hugger P, Sauder G, Panda-Jonas S, Degenring
R: Intravitreal triamcinolone acetonide for exudative age related
macular degeneration. Br J Ophthalmol (2003) 87(4):462-468.
10. Rodriguez-Coleman H, Yuan P, Kim H, Gravlin L, Srivastava S, Csaky
KG, Robinson MR: Intravitreal injection of triamcinolone for diffuse
macular edema. Arch Ophthalmol (2004) 122(7):1085-1086.
11. Penfold PL, Wen L, Madigan MC, Gillies MC, King NJ, Provis JM:
Triamcinolone-acetonide modulates permeablility and intercellular
adhesion molecule-1 (ICAM-1) expression of the ECV304 cell line:
Implications for macular degeneration. Clin Exp Immunol (2000)
121(3):458-465.
12. Penfold PL, Wong JG, Gyory J, Billson FA: Effects of triamcinolone
acetonide on microglial morphology quantitative expression of
MHC-II in exudative age-related macular degeneration. Clin
Experiment Ophthalmol (2001) 29(3):188-192.
13. Jonas JB, Kreissig I, Sofker A, Degenring RF: Intravitreal injection of
triamcinolone for diffuse diabetic macular edema. Arch Ophthalmol
(2003) 121(1):57-61.
14. Mozaffarieh M, Krepler K, Heinzl H, Sacu S, Wedrich A: Visual
function, quality of life and patient satisfaction after ophthalmic
surgery: A comparative study. Ophthalmologica (2004) 218(1):26-30.
15. Pollack A, Bukelman A, Zalish M, Leiba H, Oliver M: The course of
age-related macular degeneration following bilateral cataract
surgery. Ophthalmic Surg Lasers (1998) 29(4):286-294.
16. Van de Schaft TL, Mooy CM, de Bruijn WC, Mulder PG, Pameyer JH, de
Jong PT: Increased prevalence of disciform macular degeneration
after cataract extraction with implantation of an intraocular lens. Br
J Ophthalmol (1994) 78(6):441-445.
17. Shuttleworth GN, Luhishi EA, Harrad RA: Do patients with age related
maculopathy and cataract benefit from cataract surgery? Br J
Ophthalmol (1998) 82(6):611-616.
18. Armbrecht AM, Findlay C, Kaushal S, Aspinall P, Hill AR, Dhillon B: Is
cataract surgery justified in patients with age related macular
degeneration? A visual function and quality of life assessment. Br J
Ophthalmol (2000) 84(12):1343-1348.
19. Engelman CJ, Palmer JD, Egbert P: Orbital abscess following
subtenon triamcinolone injection. Arch Ophthalmol (2004)
122(4):654-655.
20. Nelson ML, Tennant MT, Sivalingam A, Regillo CD, Belmont JB,
Martidis A: Infectious and presumed noninfectious endophthalmitis
after intravitreal triamcinolone acetonide injection. Retina (2003)
23(5):686-691.
21. Sutter FK, Gillies MC: Pseudo-endophthalmitis after intravitreal
injection of triamcinolone. Br J Ophthalmol (2003) 87(8):972-974.

20
Nitrone spin on cerebral ischemia
Sheila A Doggrell
Address
Division of Health Practice
Auckland University of Technology-Akoranga Campus
90 Akoranga Drive
Northcote
Auckland
New Zealand
Email: s.doggrell@xtra.co.nz
Current Opinion in Investigational Drugs 2006 7(1):20-24
© The Thomson Corporation ISSN 1472-4472
Clinical trials with radical scavenging antioxidants have
shown little or no benefit in the treatment of ischemic stroke.
The spin trap nitrones covalently bind with short-lived reactive
radicals to inactivate them for longer than the conventional
scavenging antioxidants. One of these agents, NXY-059, is
effective in animal models of cerebral ischemia, and is in phase
III clinical trials for ischemic stroke by AstraZeneca, under
license from Renovis. Second-generation nitrones (azulenyl
nitrones) have also been described and shown to be
neuroprotective in animal models. Thus, at last, it seems that
antioxidants that are potent enough to have considerable
potential for the treatment of cerebral ischemia are in
development.
Keywords Animal model, azulenyl nitrone, cerebral ischemia,
clinical trial, NXY-059, PBN, S-PBN, stilbazulenyl nitrone
Introduction
Stroke is the leading cause of disability and the third leading
cause of death in the western world. Approximately 750,000
new cases occur in the US each year, and although strokes
are more prevalent in the elderly, they can occur at all ages,
and are more common in African-Americans than
Caucasians. The only pharmacological treatment for acute
ischemic stroke currently used is tissue plasminogen
activator (tPA) to dissolve the clot.
As the most common cause of ischemic stroke in humans is
an infarct in the middle cerebral artery [1], animal stroke
models should ideally involve occlusion of this artery.
Although cerebral infarcts can reperfuse, a considerable
amount of time may elapse before this occurs [2];
consequently it is appropriate to study potential
neuroprotective drugs in both transient and permanent
occlusion animal models.
The brain is a highly oxygenated organ that consumes
approximately a fifth of the total oxygen of the body, and
which derives most of its energy from oxidative metabolism
of the mitochondrial respiratory chain. It is extremely
sensitive to oxidative damage from free radicals, which
occurs during ischemia/reperfusion insult and ultimately
leads to neuronal cell death. Plasma levels of the antioxidant
vitamin C are lowered, whereas markers of oxidative stress
are increased in patients with ischemic stroke [3], indicating
that antioxidants may be useful in the prevention and
treatment of this disorder. However, antioxidant vitamin
supplementation is ineffective in preventing stroke [4], and
limited success has been achieved with free-radical
scavengers (reviewed in reference [5]).
Free-radical scavengers, such as vitamin E, donate a
hydrogen ion to a radical to form a second radical−the
tocopherol radical with vitamin E−which is relatively stable.
However, the tocopherol radical can generate radicals itself
under certain circumstances, for example, exposure to
reducing metals. Nitrone spin traps are so-called because
they covalently bind with short-lived reactive radicals, such
as hydroxyl radicals, as stable nitroxides. Historically, the
nitrones were used to identify and elucidate free radicals
and associated chemical and biological mechanisms. More
recently, the therapeutic potential of nitrones as
neuroprotective agents has been considered. In the first part
of this review, the effects of the first generation of nitrones in
animal models of cerebral ischemia are discussed. One of
these nitrones, NXY-059 (AstraZeneca plc/Renovis Inc;
Figure 1), is undergoing phase III clinical trials for the
treatment of stroke and is discussed in more detail in this
review. Finally, the second-generation nitrones, the azulenyl
nitrones, which are much more potent spin traps than the
first-generation nitrones, are considered as neuroprotective
agents in a variety of animal models, including cerebral
ischemia.
First-generation nitrones
PBN, S-PBN, MDL-101002 and S-34176
The first nitrone spin trap agent to demonstrate
neuroprotective properties was α-phenyl-tert-butyl nitrone
(PBN; Figure 1). Interestingly, it was found that nitrone spin
trap agents were effective when administered after the
ischemic event. Thus, when PBN was administered 30 min
prior to, or 30 min after, a 5-min bilateral occlusion of the
carotid artery in the gerbil, it reduced the subsequent
damage to the hippocampal CAI pyramidal cell layer [6•,7],
and this protection was associated with the ability to
prevent a cascade of free radical generation by forming spin
adducts [8]. Subsequently, PBN was shown to reduce
cortical infarction when injected before and after transient
middle cerebral artery occlusion in the rat, a standard model
of ischemic stroke [9]. In the focal embolic cerebral ischemia
model in the rat, both PBN and N-tert-butyl-(2-sulfophenyl)nitrone
(S-PBN; AstraZeneca plc/Renovis Inc; Figure 1)
reduced the neurological deficit and cerebral infarct volume
when commenced 2 h after the introduction of an
autologous thrombus into the right-side middle coronary
artery [10].
The next group of nitrone spin traps had a cyclic structure
and demonstrated improved activity over PBN. These
included MDL-101002 (Figure 1), which is more potent than
PBN in inhibiting iron-induced peroxidation in liposomes,
as well as in trapping superoxide anions and hydroxyl
radicals [11]. Furthermore, the hydroxyl radical adducts
formed with MDL-101002 had a longer half-life (5 min) than
adducts formed with PBN [11]. MDL-101002 was reported to

Figure 1. The structures of selected first generation nitrones.
C
H 3
C
H 3
HO
Na
CH 3
N +
O
S
O
O
O
S
O
OH
NXY-059
(AstraZeneca/Renovis)
Na
C
H 3
C
H 3
C
H 3
C
H 3
be neuroprotective in the transient and permanent middle
cerebral artery ligation models of stroke in rats [12],
however, there have been no further reports of its
development for the treatment of stroke.
The chemical structures of some imidazolyl nitrones have been
described [13], with the in vivo activity of one of these agents,
S-34176 (Servier; Figure 1), reported in 2005. When
administered at a dose of 75 mg/kg intraperitoneally 30 min
before transient global ischemia, S-34176 prevented delayed
neuronal death in the hippocampal CA1 area in the rat [14]. The
effects of S-34176 when administered after cerebral infarction in
an animal model have not been reported to date.
NXY-059: Animal and cellular studies
The nitrone compound that has been studied most to date is
NXY-059 (reviewed in reference [15]). In the rat transient
focal cerebral ischemia model (2 h of middle cerebral artery
occlusion), NXY-059 reduced infarct volume when
administered at 30 mg/kg/h commencing 3 to 6 h after the
start of reperfusion [16]. This agent was more water soluble
than PBN, but also proved more efficacious despite having
less ability to penetrate the blood-brain barrier (BBB) [16].
This finding suggests that one of the benefits of NXY-059 is
its ability to inhibit free radical damage to the endothelium
within the blood vessel. A subsequent study, using the same
model, showed that when NXY-059 treatment (1, 10 and 30
mg/kg/h) was commenced 2.75 h after occlusion, both the
neurological deficit (scored from forelimb flexion,
spontaneous rotation and absence of response to
contralateral whisker stimulation) and infarct size were
reduced in a dose-dependent manner at 24 h [17].
In permanent focal cerebral ischemia in the spontaneously
hypertensive rat (clip on middle cerebral artery), there was a
22.6% infarct of the contralateral hemisphere 24 h after
occlusion [18]. The infarct size was reduced to 17.4% with a
continuous infusion of NXY-059 (30 mg/kg/h) commenced
5 min after occlusion, but this did not reach significance [18].
At 60 mg/kg/h NXY-059, the infarct size was reduced to
14.5%, which was a significant reduction [18]. A subsequent
study using permanent ischemia in normotensive rats showed
that with a loading dose of 32.5 mg NXY-059 administered
subcutaneously, followed by 30 mg/kg/h of NXY-059
administered via an osmotic minipump (commenced 5 min
after occlusion), there was a reduction in the damage to the
sub-cortex, but not the cortex, and that higher doses reduced
the damaged area in both the cortex and sub-cortex
CH 3
N +
O
CH 3
N +
O
O
S
O
OH
Na
Nitrone spin on cerebral ischemia Doggrell 21
PBN S-PBN
MDL-101002
S-34176
(AstraZeneca/Renovis)
(Servier)
N +
O
CH 3
CH 3
H3C
C
H 3
CH 3
N +
O
H
N
N
F F
[17]. A further experiment showed that a 50-mg/kg/h dose
of NXY-059 gave some neuroprotection in both the cortex
and sub-cortex when the infusion was commenced 2 h after
the occlusion [17].
In humans, agents that improve functional disability after
stroke are required. Thus, the finding that NXY-059 reduces
the functional disability resulting from ischemic stroke in
monkeys was welcomed. At a dose of 28 mg/kg for 48 h,
commenced 5 min after middle cerebral artery occlusion,
NXY-059 improved the reach of monkeys with their
hemiparetic arm, lessened spatial perceptual neglect at 3 and
10 weeks, and reduced brain damage [19]. Of more interest
was a subsequent study in the monkey middle cerebral
artery occlusion model showing that if a higher dose of
NXY-059 was administered, the commencement of infusion
could be delayed for 4 h after occlusion while maintaining
the beneficial effect [20•]. In conclusion, NXY-059 treatment
ameliorated long-term motor impairment, improved the use
of the contralateral stroke-affected arm, and lessened spatial
neglect, while reducing infarct size [20•].
Several drugs that have shown efficacy in animal models of
stroke, including the γ-aminobutyric acid mimetic
clomethiazole [21] and N-methyl-D-aspartate antagonists
(eg, AR-R15896AR (AstraZeneca plc)) [22], have been
unsuccessful in clinical trials because of a lack of efficacy or
tolerability [21,22]. In the monkey model of stroke, NXY-059
was more efficacious than clomethiazole or AR-R15896AR,
producing a greater reduction in infarct size following
middle cerebral artery occlusion [23]. Of the three drugs,
only NXY-059 improved motor deficit and reduced spatial
neglect after 10 weeks [23].
At present, the only effective treatment for ischemic stroke is
the fibrinolytic agent tPA, which acts by dissolving the clot.
The efficacy of NXY-059 has been studied in embolic models
of cerebral ischemia alone and in combination with tPA; the
number of small clots that had to be administered to rabbits
to induce neurological deficits was increased by both
NXY-059 and tPA when administered alone 3 h after
external carotid ligation [24]. When used as a combination
therapy, NXY-059 and tPA had an additive effect on
increasing the number of small clots required to cause
neurological deficits [24]. Subsequently, it was shown that
the late co-administration (6 h) of NXY-059 and the synthetic
tPA tenecteplase was associated with an improvement in
behavioral deficits [25].
F

22 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
PBN has effective BBB penetration, but questions have
remained about whether NXY-059 penetrates the BBB
sufficiently for it to have a central mechanism of action. In a coculture
of endothelial cells and primary astrocytes as a model of
the BBB, uptake of PBN was high, but uptake of S-PBN and
NXY-059 was not [26]. However, the permeability of BBB by
NXY-059 increased with increasing length of ischemia,
although there was no uptake into endothelial cells [26].
In addition to acting as a spin trap for free radicals, NXY-059
may be neuroprotective by inhibiting the release of
cytochrome C, a key initiator of apoptosis. Cytochrome C
levels increased during reperfusion after a 2-h occlusion of
the rat cerebral artery, and NXY-059 treatment prevented
this increase [27].
NXY-059: Clinical studies
NXY-059 was well tolerated by healthy volunteers at an
infusion rate of 1.1 to 1.5 mg/kg/h for up to 72 h [28].
Excretion of NXY-059 occurred via the renal route and, in
individuals with renal impairment, plasma clearance was
directly proportional to glomerular filtration rate [29].
NXY-059 usually has a half-life of 2 to 4 h, but this was
extended to 10 to 12 h in individuals with moderate and
severe renal impairment [29]. Consequently, in patients with
renal impairment, the dose of NXY-059 needs to be adjusted
on the basis of creatinine clearance [29].
When administered to patients within 24 h of stroke,
NXY-059 (250 mg over 1 h, followed by 85 mg/h for 71 h, or
500 mg over 1 h, followed by 170 mg/h for 71 h) was well
tolerated [30]. In this small study of tolerability, the clinical
outcome scores were collected for descriptive purposes only,
and no improvement in clinical outcome was demonstrated
for these doses, possibly because the study was not designed
to measure efficacy [30]. Furthermore, the doses of NXY-059
used gave plasma levels (25 and 40 µmol/l) that were lower
than those associated with neuroprotection in animal studies
(200 µmol/l) [30], and thus may have been too low to be
efficacious. Subsequently, higher doses of NXY-059 were
tested in patients within 24 h of stroke onset (915 mg over 1
h, followed by 420 mg/h for 71 h, or 1820 mg over 1 h,
followed by 844 mg/h for 71 h), with the higher dose
achieving a steady-state plasma level of 260 µmol/l, which
Figure 2. The structures of STAZN and lipid- and water-soluble AZNs.
C
H 3
C
H 3
C
H 3
CH 3
N +
CH 3
O
C
H 3
CH 3
_
O
STAZN
(University of Miami)
CH 3
N +
C
H 3
CH 3
CH 3
CH 3
C
H 3
was above that associated with therapeutic benefit in
animals [31]. Furthermore, the higher doses were also well
tolerated [31]. Although these studies were not conducted to
determine effectiveness, at day 30, 58% of the 38 patients
administered the 844-mg dose of NXY-059 were assessed as
good on the Barthel Index Score, compared with 47% of
patients from the placebo group [31].
NXY-059 (as Cerovive) is currently undergoing phase III clinical
trials for the treatment of ischemic stroke. The Stroke Acute
Ischemia NXY Treatment (SAINT-1) trial is evaluating the effect
of NXY-059 on disability and neurological recovery in acute
ischemic stroke patients [32]. The Independent Data and Safety
Monitoring Board that reviewed the outcome after a 3-month
follow-up in 1000 patients recommended that the trial be
continued [32]. In May 2005, AstraZeneca announced that the
first analysis of data from the SAINT-1 trial in 1700 patients
showed a significant reduction (p = 0.038) for patients treated
with NXY-059 compared with those receiving placebo, based
on the Modified Rankin Scale for neurological impairment [33].
However, there was no significant difference between
NXY-059 and placebo on the National Institutes of Health
Stroke Scale [33].
Second-generation nitrones
Azulenyl nitrones
Azulenyl nitrones (AZNs) are a class of compounds that can
be synthesized from the natural product guaiazulene [34]
and possess oxidation potentials far lower than that of firstgeneration
nitrones [35•]. For example, the nitronylsubstituted
hydrocarbon stilbazulenyl nitrone (STAZN,
University of Miami; Figure 2) is 300-fold more potent at
inhibiting the free radical-mediated aerobic peroxidation of
cumene than PBN or NXY-059 [36•]. Furthermore, because
STAZN is lipid soluble, it is likely to cross the BBB.
STAZN has neuroprotective activity in a rat model of
traumatic brain injury. Anesthetized rats were subjected to a
right parietoccipital parasagittal fluid-percussion injury, and
neurological status was evaluated on days 1, 2 and 7 [37•]. At a
dose of 30 mg/kg, when administered 5 min and 4 h after the
trauma, STAZN improved neurological scores on days 2 and
7 compared with vehicle [37•]. The mean contusion area was
CH 3
C
H 3
_
O
CH 3
N +
O
CH3 CH3 H
O
CH 3
C
H 3
CH 3
C
H 3
_
O
CH 3
N +
H
CH3 CH3 C
H 3
H
N +
O
CH 3
lipid-soluble AZN water-soluble AZN
CH 3

4.8 mm 2 in vehicle-treated rats, which was reduced by 63%
to 1.8 mm 2 following treatment with STAZN [37•]. This
reduction was in the deep cortical contusion, with the
hippocampal cell loss in the CA3 sector being unaffected by
STAZN [37•].
STAZN was also neuroprotective in animal models of
Parkinson's disease and Huntington's disease. The
neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine
(MPTP) causes Parkinsonian syndrome in humans, and is
commonly used to create animal models of Parkinson's
disease. The toxic metabolite of MPTP accumulates in the
mitochondria of dopaminergic nerves, where it impairs
energy production and increases free radical production to
ultimately lead to dopaminergic nerve death. In the MPTP
model in mice, both a lipid-soluble and a water-soluble
azulenyl nitrone (Figure 2), administered prior to and after
MPTP administration, protected against dopamine
depletion, and were more efficacious than S-PBN [35•].
In 1998, AZNs were shown to be neuroprotective in cerebral
ischemia. The hippocampal neurons of gerbils are
particularly sensitive to ischemia, and after 7 min of bilateral
carotid occlusion followed by 5 days of reperfusion, a 70%
loss of neurons in the CA1 hippocampus resulted [34]. This
loss was reduced to 36% by an intraperitoneal
administration of 100 mg/kg of AZN 30 min prior to the
occlusion [34].
STAZN (10 or 20 mg/kg) administered intraperitoneally 30 min
before and 3, 12 and 24 h after MPTP administration, reduced
the depletion of dopaminergic nerves in the substantia nigra
pars compacta in animal models of Huntington's and
Parkinson's diseases [38•]. In this study, the mitochondrial
inhibitor 3-nitropropionic acid was used to create an animal
model of Huntington's disease. Treatment with STAZN (before
and during the administration of 3-nitropropionic acid)
reduced levels of the lipid peroxidation product
melondialdehyde and the lesion volumes [38•].
Importantly, STAZN was shown to be neuroprotective in
cerebral ischemia when administered after occlusion. A
standard neurobehavioral assessment demonstrated that
after 2 h of middle coronary artery occlusion, rats improved
modestly over a 72-h period [39••]. This improvement was
quicker and more extensive when rats were treated with
STAZN at intraperitoneal doses of 0.6 mg/kg at onset and
repeated after 2 h of reperfusion [39••]. STAZN treatment
also reduced the infarct volume, with the neuroprotection
being predominantly in the cortical region; in 13 of 22
STAZN-treated rats, the cortical infarct was almost
completely prevented [39••]. The researchers commented
that the neuroprotection seen with STAZN exceeded that
observed with many other agents in a similar model [39••].
The doses of STAZN needed for a neuroprotective effect
were 300- to 600-fold lower than those needed to induce
neuroprotection with NXY-059 [38•].
Pharmacokinetic studies showed that STAZN was slowly
absorbed after intraperitoneal injection in the rat, with a
Nitrone spin on cerebral ischemia Doggrell 23
computed half-life of 13.9 h [40]. After intravenous injection
of STAZN, a two-component decay occurred, with half-lives
of 28 min and 6.7 h [40]. STAZN permeated the brain, where
levels in the whole forebrain of the rat were 2.5% of blood
levels, and also accumulated in rat liver [40].
Conclusion
The effectiveness of free radical-scavenging antioxidants in
clinical trials for the prevention and treatment of cerebral
ischemia has been disappointing. The spin trap nitrones
covalently bind with short-lived reactive radicals to
inactivate them for longer than the conventional scavenging
antioxidants. The first nitrone spin trap agent shown to be
neuroprotective was PBN. More importantly, it was
discovered that nitrone spin trap agents were effective when
administered after onset of ischemia. One of these agents,
NXY-059, has demonstrated efficacy in animal models of
cerebral ischemia and is undergoing clinical trials for
ischemic stroke. Second-generation nitrones (AZNs) with a
greater ability to remove reactive radicals have been
investigated in studies, in which neuroprotection in animal
models of traumatic brain injury, Parkinson's disease,
Huntington's disease and cerebral ischemia have been
demonstrated. Thus, at last, it seems that potent antioxidants
that have considerable potential for the treatment of cerebral
ischemia are in development.
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Drugs in development for Parkinson's disease: An update
Tom H Johnston 1 & Jonathan M Brotchie 1,2 *
Addresses
1 Toronto Western Research Institute
Toronto Western Hospital
University Health Network
399 Bathurst Street, MC 11-419
Toronto
ON M5T 2S8
Canada
Email: brotchie@uhnres.utoronto.ca
2Atuka Ltd
37th Floor
First Canadian Place
100 King Street West
Toronto
ON M5X 1C9
Canada
*To whom correspondence should be addressed
Current Opinion in Investigational Drugs 2006 7(1):25-32
© The Thomson Corporation ISSN 1472-4472
The current development of emerging pharmacological
treatments for Parkinson's disease (PD), from preclinical to
launch, is summarized. Advances over the past year are
highlighted, including the significant progress of several drugs
through various stages of development. Several agents have
been discontinued from development, either because of adverse
effects or lack of clinical efficacy. The methyl-esterified form of
L-DOPA (melevodopa) and the monoamine oxidase type B
inhibitor rasagiline have both been launched. With regard to
the monoamine re-uptake inhibitors, many changes have been
witnessed, with new agents reaching preclinical development
and pre-existing ones being discontinued or having no
development reported. Of the dopamine agonists, many
continue to progress successfully through clinical trials.
Others have struggled to demonstrate a significant advantage
over currently available treatments and have been
discontinued. The field of non-dopaminergic treatments
remains dynamic. The α2 adrenergic receptor antagonists and
the adenosine A2A receptor antagonists remain in clinical
trials. Trials of the neuronal synchronization modulator
levetiracetam are at an advanced stage, and there has also been
a new addition to the class (ie, seletracetam). There has been a
change in the landscape of neuroprotective agents that
modulate disease progression. Candidates from the classes of
growth factors and glyceraldehyde-3-phosphate dehydrogenase
inhibitors have been discontinued, or no development has been
reported, and the mixed lineage kinase inhibitor CEP-1347 has
been discontinued for PD treatment. Other drugs in this field,
such as neuroimmunophilins, estrogens and α-synuclein
oligomerization inhibitors, remain in development.
Keywords Adenosine A2A, antiparkinsonian, monoamine
oxidase inhibitors, non-dopaminergic
Introduction
A summary of select antiparkinsonian, antidyskinetic and
neuroprotective/neurorestorative agents discussed in this
review is presented in Tables 1 to 3. For a detailed
discussion of the rationale for the majority of drugs in
development, refer to our original review [1]. It should be
25
noted that, for commercial reasons, much of the information
that relates to the development of these compounds is not
available in the public domain and our understanding is
derived from a variety of media reports of varying levels of
reliability (eg, scientific literature, websites and company
annual reports).
Antiparkinsonian symptomatic agents
In the field of antiparkinsonian therapies, the development of
two dopamine-replacing compounds, etilevodopa and
sumanirole, has been discontinued [2,3]. In both instances, it
seems that this was not due to a lack of antiparkinsonian
efficacy, but rather because of a lack of any advantage over
competing products. The discontinuation of Pfizer's sumanirole
is disappointing because it represented the first truly dopamine
D2-selective agonist [4], and thus had great promise as an agent
that might avoid some of the complications that are associated
with traditional dopamine replacement therapy, such as
dyskinesia and psychosis [5]. The reason behind the failure is
unclear, and the entirety of Pfizer's preclinical data on this agent
may never enter the public domain. However, from what has
been made public, it appears that the preclinical investigations
to define the advantageous properties of sumanirole over its
competitors, especially with respect to development/
expression of dyskinesia and/or psychosis, were quite limited.
This was particularly so in studies in 1-methyl-4-phenyl-1,2,3,6tetrahydropyridine
(MPTP) primates, where little beyond
antiparkinsonian efficacy appears to have been presented
publicly [6,7]. Clinical trials designed to maximize the potential
advantages of sumanirole might thus have been overlooked.
Another significant change in the field within the last year
is the decline in optimism regarding monoamine uptake
inhibitors. Although the concept of enhancing remaining
levels of dopamine with such compounds was supported
by studies in MPTP-lesioned marmosets [8,9], the
development of brasofensine, SPD-473 and SPD-451 has
been discontinued [10]. The reasons behind these failures
vary, but include, for example, lack of efficacy (SPD-473)
[11]. In light of these developments, the results of the
ongoing phase II trial of NS-2330 (NeuroSearch
A/S/Boehringer Ingleheim Corp) [12] and the
development of SEP-226330 (Sepracor Inc), an agent
claimed to reduce dopamine and noradrenaline, but not
serotonin, re-uptake, are awaited with interest [13].
Advances in the development of patch and controlledrelease
formulations of agonists have been made. Leading
the way are studies with the rotigotine patch (Schwarz
Pharma AG/Otsuka Pharmaceutical Co Ltd), which is at the
pre-registration stage, while the lisuride transcutaneous
patch (Neurobiotec GmbH/Prestwick Pharmaceuticals Inc)
has advanced to phase III clinical trials [14]. A controlledrelease
version of the D2 agonist ropinirole
(GlaxoSmithKline plc/SkyePharma plc) is undergoing phase
III clinical trials [15].

26 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Table 1. Examples of antiparkinsonian agents.
Compound Developing company/
institution
Class of
compound
Dopaminergic
L-DOPA inhaled
(Inhaled levodopa)
O-1369
Boston Life Sciences Inc Dopamine
(BLS-602/BLS-605)
uptake inhibitor
SEP-226330 Sepracor Inc Dopamine/
norepinephrine
reuptake
inhibitor
H
O CH 3
Cl
Cl
HO
O
O
OH O
OH
OH
Phase of
clinical
development
Other potential
actions
Alkermes Inc - Preclinical -
Reference
[35•]
Preclinical - [36]
Preclinical - [13]
Rotigotine nasal spray Schwarz Pharma AG D2 agonist Phase I Neuroprotective [37]
BIA 3202
(BIA-3-270)
BIAL Group COMT inhibitor Phase I Neuroprotective [38]
Cell therapy (dopamine
Titan
Human retinal Phase II - [39]
producers, Parkinson's)
Pharmaceuticals Inc/ pigment
(Spheramine)
Schering AG epithelial cells
on microcarrier
beads that
produce
L-DOPA
NS-2330
NeuroSearch A/S/ Monamine Phase II Cognitive [40]
H C 3
Boehringer Ingelheim reuptake
enhancement.
N H
Corp
inhibitor
Antidepressant
Ropinirole
GlaxoSmithKline plc/
(ReQuip CR)
SkyePharma plc
Lisuride transdermal patch Prestwick
Pharmaceuticals Inc/
NeuroBiotech GmbH
Safinamide
Newron Pharmaceuticals
(PNU-151774E)
SpA
N
H 2
O
CH 3
H
N
Bifeprunox
(DU-127090)
N
H
N
O
O
SLV-308
(SME-308)
CH 3
N
O
N
H
Rotigotine
(N-0923/SPM-962)
OH
N
N
N
O
O
CH 3
HCl
S
F
Solvay SA/
H Lundbeck A/S/
Wyeth Pharmaceuticals
D3/weak D2
agonist
Phase III Neuroprotective [15]
D2/D1 agonist Phase III - [14]
MAO-B
inhibitor/Na + and
K + channel
modulator
D2 partial
agonist/5-HT1A
agonist
Solvay SA D2 partial
Schwarz Pharma AG/
Otsuka Pharmaceutical
Co Ltd
agonist/5-HT1A
agonist
Phase III Neuroprotective [41,42,43••,
44]
Phase III - [45]
Phase III Antidepressant [46]
D2 agonist Pre-registered Neuroprotective [47]

Table 1. Examples of antiparkinsonian agents (continued).
Compound Developing company/
institution
Piribedil
(Trivastal)
Zonisamide
(Zonegran)
Rasagiline
(TVP-1012/Agilect (US)/Azilect
(Europe)
Drugs in development for Parkinson's disease: An update Johnston & Brotchie 27
Class of
compound
Servier D2/3 agonist/α2
antagonist
Dainippon Sumitomo
Pharma Co Ltd/
Donga Pharmaceutical
Co Ltd/Eisai Co Ltd
Teva Pharmaceutical
Industries Ltd/
Eisai Co Ltd/
H Lundbeck A/S
Complex
dopaminergic
Irreversible MAO-
B inhibitor
Zandopa
Zandu Complex
(HP-200/Mucuna pruriens)
dopaminergic
SPD-451 Shire plc Monamine
reuptake inhibitor
Brasofensine
(NS-2214)
C
H 3
N
H
SPD-473
(BTS-74398)
O CH 3
N Cl
Cl
O
O
OH
OH
NeuroSearch A/S Monamine
reuptake inhibitor
Shire plc Monamine
reuptake inhibitor
Phase of
clinical
development
Launched but
new adjunct
trials underway
Other potential
actions
Reference
- [48]
Launched Neuroprotective [49-51]
Launched Neuroprotective [52]
Launched Neuroprotective [53-56]
No development
reported
Cognitive
enhancement.
Antidepressant
Discontinued Cognitive
enhancement.
Antidepressant
Discontinued Cognitive
enhancement.
Antidepressant
Sumanirole
(PNU-95666)
Non-dopaminergic
Pfizer Inc D2 agonist Discontinued - [3]
Adenosine A2A blocker Adenosine
Therapeutics LLC
A2A antagonist Preclinical Neuroprotective [58]
Adenosine A2A receptor
Neurocrine
A2A antagonist Preclinical Neuroprotective [59]
antagonists
Biosciences Inc/
Almirall Prodesfarma
SA
V-2006 Biogen IDEC Inc A2A antagonist Phase I Neuroprotective [25]
AVE-1625 sanofi-aventis CB1 antagonist Phase I - [60]
Sch-58261 analogs Schering-Plough Corp A2A antagonist Phase II Neuroprotective [61]
Istradefylline
Kyowa Hakko Kogyo A2A antagonist Phase III Neuroprotective [62-64]
(KW-6002)
Co Ltd
CH 3
O
N
C
H 3
O CH 3
N
Aricept
(Donepezil/E-2020)
N
N
Altinicline
(SIB-1508Y)
HC
N
H
CH 3
N
O
CH 3
O
CH 3
Eisai Co Ltd/Pfizer Inc AchE inhibitor Launched
(pre-registered
for PD-related
dementia)
SIBIA Neurosciences
Inc
α4β2 selective
nicotinic agonist
No development
reported
Cognitive
enhancement
Cognitive
enhancement
AchE acetylcholinesterase, CB cannabinoid, COMT catechol-O-methyltransferase, MAO monoamine oxidase, PD Parkinson's disease.
[10]
[57]
[11]
[65]
[66]

28 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Table 2. Examples of antidyskinetic agents for Parkinson's disease.
Compound Developing
company/
institution
Fipamezole
(JP-1730)
F
CH 3
Talampanel
(Kinampa/LY-300164)
C
H 3
BP-897
(ST-280)
O
C
H 3
O
N
N
N
H
Sarizotan
(EMD-128130)
F
N
NH 2
HCl
N
H
N
NH
O
O
N
HCl
C
H 3
O
O
N
Class of
compound
Phase of
development
Other potential
actions
Juvantia Pharma Ltd α2 antagonist Phase II Extended 'on'
time
Reference
IVAX Corp AMPA antagonist Phase II Neuroprotective [68]
Bioprojet Pharma D3 partial agonist Phase II - [69]
Merck KGaA 5-HT1A agonist Phase II Extended 'on'
time
Seletracetam
(UCB-44212)
UCB SA SV2A modulator Phase II - [29]
ACP-103
ACADIA
Pharmaceuticals Inc
5-HT2A inverse
agonist
Phase II Antipsychotic [70,71]
E-2007 Eisai Co Ltd AMPA antagonist Phase II Neuroprotective [72]
Seroquel
(Quetiapine)
AstraZeneca plc 5-HT2A/C/D2/3
antagonist
Phase II for PD
(launched for
schizophrenia)
Antipsychotic [73,74]
AMPA α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid.
Intense interest is now focused on the area of monoamine oxidase
(MAO) inhibitors. In the past year, many data have accrued with
regard to the antiparkinsonian actions of the MAO-B inhibitor
rasagiline [11-15,16••], which has now been launched in the UK.
Also approved for launch across Europe under the brand name
Azilect, the results of two large clinical trials have demonstrated
that rasagiline is efficacious both as a monotherapy in early-stage
Parkinson's disease (PD) patients [16••,17••], and as an adjunct to
L-DOPA therapy in advanced PD patients with motor
fluctuations [18,19]. Preclinical data suggest a potential
neuroprotective action of rasagiline [20] that might be reflected in
the findings of the TVP-1012 in Early Monotherapy for
Parkinson's disease Outpatients (TEMPO) study. In TEMPO,
early-stage PD patients who commence treatment with rasagiline
as adjunctive therapy are associated with better outcomes at one
year than those patients who delay the start of treatment [21].
However, equally plausible explanations that are unrelated to
neuroprotection could underlie the findings of TEMPO.
Whatever the explanation, evidence is accumulating for the
initiation of rasagiline therapy early after diagnosis.
[67]
[26••]
In the field of non-dopaminergic anti-parkinsonian agents, the
spotlight remains on harnessing the undoubted potential of
adenosine A2A antagonists. Progress with istradefylline (Kyowa
Hakko Kogyo Co Ltd) remains relatively slow, although new
findings showing that its action is maintained have been
presented [22], and several phase III trials are now underway
[23,24]. Biogen Idec Inc is developing the non-xanthine A2A
antagonist V-2006 under license from Vernalis plc [25].
Development by both companies represents a potentially
powerful combination that could drive the development of
V-2006 so that it is at the same level as istradefylline within the
next year. New entrants to this field include Adenosine
Therapeutics, Neurocrine Biosciences and Almirall Prodesfarma,
although little is known about their developmental candidates
at this stage. It is not clear how the adenosine A2A field will
develop; istradefylline has prime-mover advantage at present,
but if one of the emerging molecules can build on the lessons
learned from the development of istradefylline, or prove useful
as a monotherapy and not just an adjunct to dopamine
replacement (as seems likely to be the case with istradefylline),
then this advantage could rapidly be negated.

Table 3. Examples of neuroprotective/neurorestorative agents for Parkinson's disease.
C
H 3
C
H 3
OH
Drugs in development for Parkinson's disease: An update Johnston & Brotchie 29
Compound Developing company/
Class of
Phase of Other potential Reference
institution
compound development actions
PAN-408 and PAN-527 Panacea Pharmaceuticals Inc α-Synuclein
oligomerization
inhibitors
Preclinical -
[75]
Sonic hedgehog protein
Curis Inc/
Hh agonist Preclinical -
[76]
agonists
Wyeth Pharmaceuticals
GYKI-47261 IVAX Corp AMPA antagonist Preclinical Anti-dyskinetic [77]
FR-255595 Astellas Pharma Inc PARP-1 inhibitor Preclinical - [78]
CERE-120
(Neurturin)
Ceregene Inc GDNF analog Phase I - [79]
MX-4509
(MITO-4509)
MIGENIX Inc Estrogen analog Phase I/II - [80]
Cereact
Ono Pharmaceutical Co Ltd/ Astrocyte modulator Phase II for PD
-
[81,82]
(ONO-2506/arundic acid)
Merck & Co Inc
(phase III for
O
cerebral
infarction)
PYM-50028
(P-63)
Phytopharm plc Not known Phase II - [83]
GPI-1485 MGI Pharma Inc/Symphony Neuroimmunophilin Phase II -
[84]
Neuro Development Co
ligand
SR-57667 sanofi-aventis Non-peptide
neurotrophic
Phase IIb Neuroprotective [85]
Creatine
Avicena Group Inc Mitochondrial
Phase III
[86]
NH
permeability
-
H N 2 N
OH
transition pore
inhibitor
CH 3
Liatermine
(GDNF)
Omigapil
(CGP-3466/TCH-346)
H C 3
N
O
O
CH
Amgen Inc Endogenous
neurotrophic factor
Discontinued -
[30]
Novartis AG GAPDH inhibitor Discontinued - [87]
AMPA α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, GAPDH glyceraldehyde-3-phosphate dehydrogenase, GDNF glial-derived
neurotrophic factor, PARP poly(ADP-ribose) polymerase, PD Parkinson's disease.
Antidyskinetic agents
Developments in the field of non-dopaminergic
antidyskinetic drugs have generally been positive. Two
agents, the α2 adrenoceptor antagonist fipamezole
(Juvantia Pharma Ltd) and the 5-hydroxytryptamine (5-
HT)1A agonist sarizotan (Merck KGaA) [26••], have both
successfully demonstrated antidyskinetic efficacy in phase
IIa studies. Preparations for phase III trials of sarizotan are
now underway [27]. It is unclear as to how UCB SA
intends to develop the anticonvulsant levetiracetam for L-
DOPA-induced dyskinesia, since it has been suggested
that there will be significant issues of tolerability owing to
somnolence [28]; however, if it can be tolerated in an
individual, antidyskinetic actions are achievable.
Preclinical data on a next-generation analog of
levetiracetam, seletracetam (UCB SA), have been reported
[29], demonstrating the apparent commitment of UCB to
both the target and therapeutic area.
Neuroprotective/neurorestorative agents
In the research of disease-modifying compounds, many
potential agents continue to vie for the opportunity to
demonstrate efficacy. The field remains characterized by a
lack of any single target recognized as being more favorable
than another, and the likelihood that several classes of
compounds will eventually occupy this space may become a
reality. The logistics of conducting clinical trials of diseasemodifying
agents remain challenging [30], and development
of some compounds for PD has been discontinued, for
example, the glial-derived neurotrophic factor, liatermine
(Amgen Inc) [31]; the neurotrophin synthesis-enhancer,
mixed lineage kinase inhibitor CEP-1347 (Cephalon Inc/H
Lundbeck A/S/ Kyowa Hakko Kogyo Co Ltd) [32]; and the
glyceraldehyde-3-phosphate dehydrogenase inhibitor
TCH-346 (Novartis AG) [33]. In a similar manner to
rasagiline, much attention has also been focused on the
neuroprotective potential of other pre-existing symptomatic

30 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
antiparkinsonian agents. For example, data were recently
presented in support of a protective action of rotigotine
whereby the progression of disability was attenuated in those
patients with early-stage PD who received this agent [34].
Conclusion
In conclusion, the area of drug development in PD remains
active and there is realistic hope of new therapies reaching
the market in the short to mid term.
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32 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
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The mechanism of action of gabapentin in neuropathic pain
J Kenneth Baillie* & Ian Power
Address
Department of Anaesthesia, Critical Care and Pain Medicine
University of Edinburgh
Royal Infirmary of Edinburgh
51 Little France Street
Edinburgh
EH16 4SA
UK
Email: j.k.baillie@doctors.org.uk
*To whom correspondence should be addressed
Current Opinion in Investigational Drugs 2006 7(1):33-39
© The Thomson Corporation ISSN 1472-4472
Neuropathic pain is a common and potentially treatable cause
of considerable lifelong morbidity. Effective pharmacological
treatments are scarce, but one group of drugs that has shown
promise is the antiepileptics. Gabapentin has become popular as
a first-line treatment for neuropathic pain because of its
efficacy as an antineuropathic agent and relatively benign sideeffect
profile. However, its mechanism of action is far from
clear. This review discusses the available evidence for the
postulated mechanisms of action of gabapentin. Understanding
the mechanism of action of this agent may well lead to the
development of safer and more effective antineuropathic drugs.
Keywords Allodynia, hyperalgesia, gabapentin,
γ-aminobutyric acid, mechanism of action, neuropathic pain,
voltage-gated calcium channel
Introduction
Neuropathic pain results from abnormal firing of damaged
peripheral nerves, often associated with direct nerve injury
or nerve damage from diabetic, post-herpetic or alcoholic
neuropathy. It has a considerable socioeconomic impact [1],
affecting more than 500,000 people in the UK alone [2], the
great majority of whom will require lifelong drug treatment
to control otherwise intolerable suffering. There has been
much recent interest in novel anti-epileptic agents as
potentially useful treatments for neuropathic pain. This
review will summarize the available evidence regarding the
mechanism of action of one such anti-epileptic drug,
gabapentin (Figure 1).
The etiologies of neuropathic pain are distinct from
nociceptive pain, and several drugs that are effective for one
type of pain are relatively ineffective for the other.
Neuropathic pain may be entirely independent of any
peripheral nerve stimulus, or it may be manifest as an
abnormal sensation of pain in response to stimulation of
other sensory modalities. A series of gene transcription
factors are activated leading to a wide range of phenotypic
alterations, including a reduction in the inhibitory
neurotransmitter γ-aminobutyric acid (GABA), downregulation
of GABA receptors [3••], and loss of GABAergic neurons [4].
At a cellular level, there are many physiological and
biochemical similarities with epilepsy. Direct injury to the
peripheral nerves leads to recurrent abnormal ectopic
33
discharges [5,6], and many of the excitatory neurotransmitters
released in neuropathic pain are also implicated in the
propagation of seizure activity. Alterations in membrane ion
channels can be found in both conditions, predisposing the
membranes to abnormal depolarization [7••]. Furthermore,
anti-epileptic medications are often also effective in the
treatment of neuropathic pain [8].
Designed as an analog of GABA that would cross the bloodbrain
barrier [9], gabapentin (1-(aminomethyl)-cyclohexane
acetic acid) was originally marketed worldwide as an antiepileptic.
Other anti-epileptics, such as carbamazepine and
phenytoin, have also been effective treatments for neuropathic
pain [8]. The main problem with the use of these older antiepileptics
is the wide range of side effects. When gabapentin
was also found to have antineuropathic activity, it quickly
became popular because of its relatively mild and dosedependent
side-effect profile, and annual worldwide sales
are now in excess of US $2 billion [10•]. Other new
anticonvulsants, such as pregabalin (Figure 1), a structural
analog of gabapentin, may also prove to be useful
treatments in neuropathic pain [11].
Figure 1. The structures of gabapentin and pregabalin.
NH 2
O
OH
C
H 3
N
H 2
CH 3
gabapentin pregabalin
Efficacy, safety and pharmacokinetics
Gabapentin is effective in reducing pain-related behavior
patterns in a variety of animal models of neuropathic pain,
including static allodynia [12], mechanical hyperalgesia [13],
thermal hyperalgesia [13], mechanical allodynia [14,15] and
thermal allodynia [16]. In humans, gabapentin reduces
neuropathic pain caused by diabetes mellitus [17], postherpetic
neuralgia [18], cancer [19] and a variety of other
neuropathic pain syndromes [20]. Gabapentin is ineffective
in acute post-operative pain following mastectomy [21] and,
interestingly, the analgesic efficacy of this agent is
dependent on the presence of some pathological state, such
as nerve injury or inflammation [22]. A recent systematic
meta analysis of randomized, controlled trials of gabapentin
yielded a combined number of patients needed to treat
(NNT) with the drug for an improvement in neuropathic
pain of 4.3 [10•], comparable with those for carbamazepine
and phenytoin [8].
There is also encouraging evidence of an additive effect of
gabapentin with other antineuropathic and analgesic agents
in rat models of neuropathic pain [12,23,24] and healthy
human volunteers [25]. Furthermore, gabapentin prevents
the development of opiate tolerance in rats [26]. In an
elegantly designed clinical trial, Gilron et al showed that the
O
OH

34 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
combination of gabapentin and morphine achieves a
significant further reduction in pain scores in a large
majority of patients with neuropathic pain [27•].
Importantly, gabapentin has relatively minor side effects
and, as supported by the data from the available trials,
withdrawal of treatment owing to side effects has not been
significantly more common than in placebo groups. The
numbers needed to harm (NNH) for minor harm (tolerable
adverse effects) was 3.7. The relative frequencies of adverse
effects included dizziness (24%), somnolence (20%),
headache (10%), diarrhea (10%), confusion (7%) and nausea
(8%) [18]. Dose titrations up to 3600 mg/day have been used
in trials, although the maximum licensed dose in the UK is
1800 mg/day. The available evidence suggests little
potential for adverse interactions with other agents.
Although gabapentin exists at physiological pH as a
zwitterion, and hence would be expected to exhibit limited
permeability across membrane barriers, radiolabeling
studies have shown that it accumulates rapidly within
neuronal cytosol [28]. This accumulation may be explained
by the carriage of gabapentin by system L amino acid
transporters, which operate across gut membranes [29] and
neuronal and glial cell membranes [30]. This system
becomes saturated at higher doses, which accounts for the
non-linear relationship between oral doses and plasma
concentration [29]. Gabapentin competes with amino acids
such as L-leucine, L-phenylalanine and L-valine at this
transporter [30], although this is unlikely to be directly
related to its mechanism of action [15].
Gabapentin exhibits very little protein binding [31] and is
excreted unchanged by the kidneys, with a first-order
elimination pattern. Its plasma half-life is predictable and
correlates with creatinine clearance [32].
Anatomical site of action
Binding sites for gabapentin are concentrated in the outer layer
of the rat cerebral cortex [33] and in the superficial laminae of
the dorsal horn [34••]. Peak anti-epileptic activity in rats occurs
approximately 2 h after peak brain interstitial concentration
[28]. The time course of antineuropathic activity after
intrathecal injection is similar [35], suggesting that intraneural
transport is prerequisite for both actions of gabapentin.
In isolated slices of rat brainstem, gabapentin inhibits
substance P-mediated release of the excitatory neurotransmitter
Figure 2. The structures of anti-epileptic drugs used to treat neuropathic pain.
O
H
N
N
H
O
N
H N 2 O H N N
2
Cl
Cl
N
N
glutamate [36]. Furthermore, in vivo experiments have
shown that gabapentin prevents the release of excitatory
neurotransmitters, including glutamate, in spinal cord
microdialysate following nociceptive stimulation by
intraperitoneal acetic acid [37] or neuropathic pain caused
by sciatic nerve ligation [13].
Possible mechanisms of action
Does the mechanism of antineuropathic action of gabapentin
differ from its anti-epileptic action? Until both mechanisms
are elucidated, we can infer from the widely differing
chemical structures of those anti-epileptic drugs that are
used for neuropathic pain (gabapentin, phenytoin,
carbamazepine, lamotrigine, clonazepam and valproate;
Figure 2) [10•] that it is unlikely that they all act at the same
site. It would therefore be unlikely that all of these drugs
each act at two distinct sites to produce two different, but
common, effects; control of seizures and relief of
neuropathic pain. Given the relative specificity of these
agents for neuropathic pain, and the epileptiform activity
observed in damaged sensory afferent fibers [5], it seems
more plausible that both effects are mediated through a
single mechanism of action.
Receptor-mediated actions
Although gabapentin was originally designed as an analog of
the central inhibitory neurotransmitter GABA [9], no conclusive
evidence has been found of a direct interaction with any of the
key receptors in central pain transmission. Initial studies
demonstrated that it has no direct agonist activity at GABA
receptors [38] and does not bind with high affinity to any
GABA receptor subtype [39••]. More recent investigations
using cloned receptors have found evidence of selective agonist
activity at a subtype of presynaptic GABAB receptors on
excitatory neurons [40•] (discussed below).
Although D-serine, which acts as an agonist at the inhibitory
glycine binding site on N-methyl-D-aspartate (NMDA)
receptors, reverses some of the actions of gabapentin [41], it
has been shown that gabapentin itself does not directly
interact with the glycine-NMDA complex [39••,42] and
gabapentin reduces downstream excitatory neurotransmitter
release from rat brain slices, even after NMDA receptorblocking
drugs have been administered [43]. Finally,
gabapentin exhibits a profound synergistic anti-allodynic
action with the AMPA receptor antagonist 6-cyano-7nitroquinoxaline-2,3-dione
(CNQX) [35], suggesting that the
two drugs do not act at the same site.
NH 2
H
N
N N +
O
phenytoin carbamazepine lamotrigine clonazepam valproate
O
Cl
O
C
H 3
O
OH
CH 3

A specific binding site on voltage-gated Ca 2+
channels
The search for the site of action of the new anti-epileptic
agent was significantly advanced by Suman-Chauhan et al,
who identified a new, high-affinity binding site for
gabapentin in rat brain homogenate [39••]. Interestingly,
the binding of gabapentin to this site was dependent on
the system L transporter, suggesting that gabapentin may
have to cross a cell membrane in order to take effect. The
binding site has been identified as the α2δ subunit of
voltage-gated Ca 2+ channels [34••]. This auxiliary subunit
is upregulated after nerve injury [44-46] and, when coexpressed
with the α1 subunit, brings about a substantial
increase in transmembrane Ca 2+ current [47]. The influx of
Ca 2+ ions through voltage-gated Ca 2+ channels is
necessary for excitatory neurotransmitter release (see
Figure 3) [48-50]. The α2δ subunit has been the subject of
much recent interest as a potential target for novel drug
development [51].
Figure 3. Relevant mechanisms of pain transmission in dorsal columns.
GABA γ-aminobutyric acid, NMDA N-methyl-D-aspartate [7••,40•,49,57••,60••,82].
The mechanism of action of gabapentin in neuropathic pain Baillie & Power 35
A gabapentin analog, 3-methyl gabapentin, has one isomeric
form with high affinity at α2δ subunits and another with much
lower affinity. Field et al have shown that the high-affinity
isomer is an effective antineuropathic agent, whereas the lowaffinity
isomer did not have antineuropathic activity in two
different rat models [52].
Gabapentin binds to α2δ subunits [34••,53] and inhibits highthreshold
neuronal Ca 2+ currents [54,55], and in cultured dorsal
root ganglion cells, whole-cell Ca 2+ current is reduced by this
agent [56]. Gabapentin-mediated Ca 2+ channel blockade
appears to preferentially affect presynaptic P/Q-type voltagegated
Ca 2+ channels, reducing the release of the excitatory
amino acids glutamate and aspartate; this effect occurs at
therapeutically relevant concentrations in rat [57••] and human
brain [43]. As the α2δ subunit is expressed in all subtypes of
voltage-gated Ca 2+ channels [58], the apparent selectivity of
gabapentin for P/Q-type channels [57••] does not fit with the
hypothesis that gabapentin acts by directly inhibiting Ca 2+
channels, and has yet to be explained.

36 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Several studies have shown that magnesium chloride and the
synthetic polyamine spermine inhibit the binding of gabapentin
to high-affinity binding sites, presumably α2δ subunits, in rats
[39••], mice [59] and pigs [42]. Intrathecal infusion of
magnesium chloride effectively attenuates the anti-allodynic
effect of gabapentin in a rat model [60••]. Nevertheless, the role
of the α2δ subunit in the antineuropathic action of gabapentin is
far from clear. Spermine had no effect on the efficacy of
gabapentin in the same study [60••]. Furthermore, both
magnesium chloride and spermine can promote gabapentin
binding to purified α2δ subunit protein and appear to have a
temperature-dependent effect on the drug in mice, stimulating
binding at 30°C, and inhibiting binding at 4°C [59]. Finally, both
magnesium chloride and spermine are allosteric modulators of
NMDA receptors and could interact with gabapentin through a
different site altogether [61].
K + channel activation
There have been some reports that gabapentin activates
inwardly rectifying K + channels, resulting in membrane
hyperpolarization and decreased excitability [40•,62]. Ng et
al found that gabapentin activates post-synaptic K + currents
in rat brain slices and Xenopus oocytes [40•]. However, this
activation was dependent on expression of a specific cloned
GABAB receptor subtype (gb1a-gb2). Furthermore, GABA
had a similar effect on Xenopus oocytes expressing GABAB
receptors, suggesting that activation of K + currents is a
receptor-mediated effect.
Selective agonism at GABAB receptors (gb1a-gb2)
GABA receptors are of two types; the multi-subunit chloride
channel receptor GABAA subtype, at which gabapentin does
not bind in significant quantities [39••], and the G-proteincoupled
GABAB receptor [63]. Although several studies have
not found that gabapentin binds to any subtype of GABAB
receptors to a significant degree [39••,64••,65], one group has
provided evidence that expression of gb1a-gb2 GABAB
receptors is prerequisite for gabapentin to alter membrane ion
permeability [40•,66]. This is of particular interest because
agonism at GABAB receptors may account for both the
gabapentin-mediated inhibition of voltage-gated Ca 2+ channels
and activation of inwardly rectifying K + channels [67••,68].
A recent pharmacological study provides further evidence
that an important interaction occurs between gabapentin
and the subtype of GABAB receptors constitutively
expressed on pre-synaptic regions of excitatory interneurons
to inhibit excitatory neurotransmitter release [69••].
Importantly, GABAergic neurons were spared, and the
effect of gabapentin on excitatory neurotransmitter release
was sensitive to specific GABAB receptor antagonists. It is
possible that GABAB receptor blockade prevented
gabapentin action by indirect physiological antagonism [70],
as residual GABA is likely to have been present in the rat
brain slices used for this experiment. However, this
postulation does not explain the direct effect of gabapentin
on a GABAB subtype expressed on Xenopus oocytes [40•].
Increased GABA synthesis or release
GABA is an important inhibitory neurotransmitter with
numerous pharmacological interactions [71]. Blockade of
GABA causes hypersensitivity and allodynia consistent with
neuropathic pain [72], and partial nerve injury reduces
dorsal horn synaptic inhibition owing to apoptosis of
GABAergic interneurons [4]. As discussed previously,
gabapentin does not have a direct action at GABAA receptors
[38], GABA-receptor-blocking drugs do not alter the
antineuropathic efficacy of gabapentin [73], and gabapentin
has no effect on GABA reuptake [74]. However, synthesis
and release of GABA in the brain are increased by
gabapentin [75,76], and magnetic resonance imaging
spectroscopy of epileptic patients taking gabapentin
demonstrated a global increase in brain GABA [77]. This
observation may be because of inhibition of GABAtransaminase
[78], activation of glutamic acid decarboxylase
[79] that is sufficient to increase GABA synthesis by 50 to
100% [80], or promotion of non-vesicular GABA release [81].
In an interesting contrast with the finding of Parker et al that
gabapentin acts on pre-synaptic GABAB receptors to inhibit
excitatory neurotransmitter release while sparing
GABAergic neurons [69••], gabapentin increased the
extrasynaptic NMDA-mediated current in GABAergic, but
not non-GABAergic, neurons in a rat model of inflammatory
pain [82,83]. This action may increase activity in inhibitory
spinal cord interneurons, thus releasing GABA under
conditions associated with neuropathic pain. However,
neither NMDA receptor modulation [60••] nor GABA
receptor blockade [73] significantly alters the efficacy of
gabapentin in rat models of pain.
Increase in peripheral whole-blood serotonin
Mood has a profound effect on perception of pain [84], so it
is a realistic possibility that some of the analgesic effects of
gabapentin in humans may be mediated by global
serotonergic activation [85]. Indeed, gabapentin has been
used to treat a variety of mood and anxiety disorders,
although randomized clinical trials have so far been
disappointing [86]. Direct evidence from rats has
contradicted this postulated mechanism; neither pretreatment
of rats with a central nervous system serotonindepleting
compound [73] nor blockade of serotonin
receptors [87] had any effect on the antihyperalgesic efficacy
of gabapentin. We conclude that serotonin is unlikely to be
central to the mechanism of action of gabapentin.
Conclusions
Despite its original conception as a drug designed to mimic
a specific neurotransmitter, gabapentin has become widely
established in clinical practice without a satisfactory
explanation of how it works. As summarized above, debate
regarding its mechanisms of action now centers on the
apparent discrepancy between the high-affinity binding site
on α2δ subunits of voltage-gated Ca 2+ channels [34••], and
persuasive evidence of a direct action at GABAB receptors
[40•].
It has been difficult to distinguish between direct effects of
the drug at Ca 2+ channels and receptor-mediated inhibition
of Ca 2+ current because of an apparently ubiquitous
physiological interdependence. Both actions occur at
therapeutically relevant concentrations, and both may

prevent the release of excitatory neurotransmitters and thus
account for the mechanism of action of gabapentin in
neuropathic pain. The presence of a high-affinity binding site
for gabapentin on Ca 2+ channels, and the fact that the
obliteration of the effect of gabapentin when binding at this site
is prevented [60••], constitute persuasive evidence in favor of a
direct effect on Ca 2+ channel activity. However, the deliberate
structural similarity with GABA, and the demonstration that
gabapentin can mimic the effect of GABA on a cloned subtype
of GABAB receptors to alter membrane ion permeability [66],
suggest that the mechanism of action of gabapentin may be
much closer to that for which it was originally designed. Even
before the mechanism of action of gabapentin has been fully
elucidated, the candidate mechanisms described here may
become rich resources for novel drug development.
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40 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
5-HT1A receptor activation: New molecular and neuroadaptive mechanisms
of pain relief
Francis C Colpaert
Address
Institut de Recherche Pierre Fabre
3 rue des Satellites
BP 94244
31432 Toulouse Cedex 4
France
Email: francis.colpaert@pierre-fabre.com
Current Opinion in Investigational Drugs 2006 7(1):40-47
© The Thomson Corporation ISSN 1472-4472
Guided by an understanding of signal transduction in painprocessing
systems, high-efficacy 5-hydroxytryptamine (5-
HT)1A receptor activation, by means of F-13640, has been
discovered as a new molecular mechanism of pain relief in
laboratory animals, inducing two neuroadaptive phenomena.
Firstly, this activation cooperates with nociceptive stimulation,
paradoxically causing analgesia, and secondly, inverse
tolerance develops so that the resulting analgesia grows rather
than decays. As an apparent result of these novel
neuroadaptive mechanisms, F-13640 exerts an analgesic action
in rat models of acute, tonic and chronic nociceptive pain that
is rivaled only by large doses of high-efficacy µ-opioid receptor
agonists. In models of neuropathic allodynia of peripheral or
central origin, chronic F-13640 administration causes an
analgesia that surpasses that observed with morphine or other
agents exemplifying other central nervous system drug
mechanisms of pain relief (eg, ketamine, imipramine and
gabapentin). Indeed, F-13640 produces long-lasting, preemptive
and, most remarkably, curative-like actions in
neuropathic allodynia. Although awaiting proof-of-concept
evidence in humans, high-efficacy 5-HT1A receptor activation
may uniquely challenge the opioids for pain therapy.
Keywords 5-HT1A receptors, analgesia, neuropathic pain,
nociceptive pain, opioids, tolerance
Introduction
Neuroanatomical and physiological studies have long
implicated serotonin (5-hydroxytryptamine; 5-HT) in the
central nervous system (CNS) control of pain (eg, descending
inhibition) [1], and while a host of 5-HT receptors are known to
mediate the cellular actions of serotonin [2], the 5-HT1A
serotonin receptor subtype has not traditionally been
considered as a molecular target for pain therapy [3-8].
However, it will be argued here that high-efficacy activation of
CNS 5-HT1A receptors may perhaps now begin to challenge the
opioids as an option for the treatment of pain, although the
latter have been the mainstay treatment of pain for over
thousands of years. Somewhat ironically, this stark
development results from studies into opioid tolerance in the
1970s, and from a well-accepted concept that attempted to
account for tolerance to opioid analgesia.
Signal transduction in pain-processing systems
The concept accounting for opioid analgesia tolerance specifies
that any input to pain-processing systems causes not a single
effect, but dual effects that are bidirectional, or opposite, in sign
[9,10•,11,12]. Thus, morphine causes not only analgesia as a
'first-order' effect, but also a 'second-order' hyperalgesia that
outlasts opioid receptor activation for some time. The first-order
analgesia results directly from receptor activation, but the
second-order effect is an indirect consequence of this analgesia
and follows in time. Upon chronic opioid exposure, the secondorder
pain, or sensitization to nociceptive input, grows and
counteracts the first-order analgesia. Thus, opioid tolerance is
due, paradoxically, to opioid pain [10•,13,14].
Intriguingly, the concept of high-efficacy activation of 5-HT1A
receptors as an option for the treatment of pain suggested that a
mechanism wholly different from opioid receptor activation
could possibly exist, whereby analgesia could be produced.
Indeed, according to this concept, the stimulation of peripheral
nociceptors would initially produce pain as a first-order effect,
but also hypoalgesia as a second-order effect; with chronicity,
this second-order hypoalgesia should grow, counteract the firstorder
pain and, remarkably, develop into an increasingly
powerful analgesia (ie, inverse tolerance). Of equal importance,
according to the concept, is that one nociceptive stimulation
should cooperate with another, concomitant stimulation of
nociceptors to paradoxically induce second-order hypoalgesia
[4,9]. The potential of such an intervention is considerable; it
would be most effective in the treatment of severe pain and
would resolve inaccessible, opioid-resistant, chronic pains.
Thus, since the 1970s, researchers currently at Pierre Fabre SA
have employed an increasing array of neuropharmacological
tools in an attempt to identify a mammalian protein and a
molecular action by which the central effects of peripheral
nociceptive stimulation can be mimicked. This protein should
initiate the neuroadaptive mechanisms of inverse tolerance and
nociceptor cooperation, and its effects should constitute the
opposite of those of opioids. 5-HT1A receptor activation has
now been identified as the neuropharmacological intervention
whereby those neuroadaptive and therapeutic objectives can
possibly be achieved [15•].
F-13640
F-13640 (Pierre Fabre SA; Figure 1) is a newly synthesized
methylamino-pyridine that has nanomolar and selective affinity
for both rat and human G-protein-coupled 5-HT1A receptors; at
1000-fold higher concentrations the compound does not interact
with many other neurotransmitter receptors, uptake sites, ion
channels and enzymes. Importantly, F-13640 has strong activity
at 5-HT1A receptors and stimulates [ 35S]GTPγS binding by a
magnitude far greater than that observed with the 5-HT1A
agonists buspirone and 8-hydroxy-2-di-n-propylamino-tetralin
(8-OH-DPAT), and more recently identified selective 5-HT1A
agonists [15•,16,17]. This combination of potency, selectivity
and high efficacy can also be observed in vivo; after
intraperitoneal injection in rat, F-13640 readily penetrates the
brain [18], inhibits spinal-cord-wide dynamic neuron and
single motor unit responses to nociceptive electrical
stimulation [19], and exerts analgesia from (ED50) doses of
0.029 mg/kg upwards [20•]. Its effects are consistently

antagonized by the selective 5-HT1A antagonist WAY-100636
[15•,20•,21,22] and the amplitude of its 5-HT1A receptormediated
actions is unrivaled by other selective 5-HT1A
receptor ligands [15•,20•].
Figure 1. The structure of F-13640.
C
H 3
N
N
H
O
F-13640
(Pierre Fabre)
Cooperation and inverse tolerance: Acute
actions
Studies have probed the sensitivity of normal rats to
nociceptive stimulation by means of the Randall-Selitto
technique, which determines the threshold mechanical
stimulation of the hindpaw required to induce vocalization
[15•]. While a subcutaneous injection of 5 mg/kg morphine
produced an initial hypoalgesia followed by hyperalgesia, 0.63
mg/kg of intraperitoneal F-13640 caused hyperalgesia followed
by hypoalgesia; these data indicate bidirectional signal
transduction and 5-HT1A receptor activation-producing effects
that are the inverse of µ-opioid receptor activation. Repeated
injection of morphine caused hyperalgesia and tolerance to its
analgesic effect; repeated F-13640 injection caused hypoalgesia
and tolerance to its pro-algesic effect. After a 2-week
subcutaneous infusion of either 5 mg/day morphine or 0.63
mg/day F-13640, rats demonstrated a normal sensitivity to the
mechanical stimulation. In morphine-infused animals, acute
injection of the opioid antagonist naloxone at this point caused
hyperalgesia; mirroring this action, the injection of the 5-HT1A
antagonist WAY-100635 in F-13640-infused animals caused
powerful hypoalgesia [15•]. The latter finding offers a stark
demonstration of the second-order nature of the analgesic effect
of F-13640 and initial evidence that high-efficacy 5-HT1A
receptor stimulation may exert a pre-emptive action on pain of
nociceptive origin.
As discussed, an acute, intraperitoneal injection of F-13640
initially produces hyperalgesia. Remarkably, and
demonstrating cooperation, at the same time after the injection
of the same dose of F-13640, the compound produces analgesia
in rats receiving an intraplantar formalin injection in a model of
tonic nociceptive pain. Similar pro- and hypoalgesic effects
occur with a host of other 5-HT1A receptor ligands [15•] in a
manner that is behaviorally specific [23]. However, the
magnitude of both of these effects depends on the extent to
which the ligands activate the receptor; thus, the low-efficacy
5-HT1A agonist buspirone is essentially inactive, and
F-13640 produces profound effects. These agents and another
seven 5-HT1A receptor ligands produced pro- and hypoalgesic
effects with a rank order that correlates highly (p < 0.001) with
the extent to which they stimulate [ 35S]GTP-γS binding [15•].
Indeed, with the exception of the high-efficacy opioid agonist
morphine, none of the available analgesics exerting their actions
by peripheral or central mechanisms rivals the magnitude of
N
F
Cl
F
5-HT1A receptor activation Colpaert 41
analgesia that F-13640 produces in this model [20•]. Tables 1
and 2 provide comparative data on the ability of various agents
to inhibit formalin-induced paw licking and paw elevation,
respectively [20•]. Although several agents inhibited paw
licking to varying degrees, only F-13640 fully inhibited both
behaviors at the early and late phases after formalin injection.
Formalin injection causes c-Fos protein expression in spinal
cord dorsal horn neurons as well as pain behaviors; an
intraperitoneal dose of morphine as high as 20 mg/kg is
required to match the extent to which 0.63 mg/kg of
intraperitoneal F-13640 suppresses formalin-induced c-Fos
protein expression [24].
The exceptionally powerful analgesia that F-13640 produces in
the formalin model of tonic nociceptive pain led the research
group to examine its possible effectiveness for intra- and postoperative
pain associated with orthopedic surgery in rats that
received an incision of the skin, fascia and plantar muscle of the
foot [25], and underwent drilling of a hole in the calcaneus [26].
As with a pre-operative intraperitoneal injection of the shortacting
opioid remifentanil (0.63 mg/kg), the same dose of
intraperitoneal F-13640 lowered the requirement for intraoperative
isoflurane anesthesia, indicating that the
5-HT1A agonist exerted analgesia equivalent to that of the
opioid in this model. When administered after surgery, F-13640
suppressed post-operative pain behaviors (ie, paw flexion and
elevation) in a lasting manner; in contrast, remifentanil
produced a short-lived analgesia that was followed by a longerlived
hyperalgesia [22]. The peri-operative use of opioids in
humans often produces a hyperalgesia and tolerance that have
been well documented in the immediate postoperative episode
[27-29]. However, surgery conducted under opioid analgesia
may also be followed by a chronic pain state [30,31] that may
perhaps result from long-lasting opioid (second-order)
hyperalgesia. Thus, high-efficacy 5-HT1A receptor activation
might rival the intra- and post-operative analgesia that is offered
by opioids and also obviate (and pre-empt) the short- and longterm
increases in post-operative pain that opioids may induce.
Long-term neuroadaptive actions
The studies considered here examined the effects of agents that
were continuously infused by means of subcutaneously
implanted osmotic pumps, for 2 weeks or longer, in rats that
were subjected to manipulations that model chronic pain of
nociceptive or neuropathic origin.
Chronic nociceptive pain
The oral self administration of a fentanyl solution offers a
measure of the spontaneous, persistent and severe chronic
nociceptive pain that is associated with adjuvant arthritis in the
rat [32]. While normal rats demonstrate hyperalgesia early after
F-13640 (0.63 mg/day) pump implantation, the agent produces
a dose-dependent, full analgesia in arthritic rats that is at least
equivalent to that found with 5 mg/day of morphine [15•],
the dose at which morphine produces dependence. The
finding that 2 weeks of morphine treatment produces
analgesia is surprising, because in normal rats the same
treatment results in complete analgesic tolerance within 8 h
of pump implantation [15•]. However, the concept that
guided this research also suggests that nociceptive
stimulation hampers the development of opioid tolerance in

42 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Table 1. Quantification of the ability of various analgesic agents to inhibit formalin-induced paw licking during the early and late phases following intraplantar formalin injection in
rats.
Drug Dose range Inhibition of formalin-induced paw licking
Early phase Late phase
ED50 95% CL MSD Lowest mean score ED50 95% CL MSD Lowest mean score
Morphine 1.25 to 40 2.4 1.1 to 5.4 10 1 ± 0.49 (10) < 1.25 - 1.25 0 ± 0 (10)
Buprenorphine 0.01 to 10 0.25 0.051 to 1.1 0.63 0.86 ± 0.46 (2.5) 0.051 0.0075 to 0.35 0.16 0.43 ± 0.3 (0.63)
Imipramine 2.5 to 40 7.6 2.5 to 23 10 0 ± 0 (40) 3.6 1.5 to 8.6 10 0 ± 0 (40)
Amitryptyline 2.5 to 40 15 7.5 to 30 10 0 ± 0 (40) 5.1 3 to 8.7 10 0 ± 0 (40)
Paroxetine 2.5 to 40 13 6 to 28 10 0.57 ± 0.29 (40) 4.4 1.2 to 16 10 0 ± 0 (40)
Aspirin 160 > 160 - > 160 5 ± 0.62 (160) > 160 - 160 5.8 ± 0.59 (160)
Diclofenac 40 to 160 > 160 - 160 0.86 ± 0.34 (160) > 160 - 160 0 ± 0 (160)
Paracetamol 10 to 160 > 160 - > 160 4.7 ± 0.61 (160) 93.1 a 9.9 to 872 160 4.0 ± 1.2 (160)
Rofecoxib 40 to 160 > 160 - > 160 5.7 ± 0.42 (40) > 160 - > 160 6.7 ± 0.57 (40)
Celecoxib 40 to 160 > 160 - > 160 5.1 ± 0.7 (40) > 160 - > 160 5.4 ± 0.78 (40)
Gabapentin 10 to 640 > 640 - 40 4.1 ± 0.86 (40) < 10 - 10 2.3 ± 0.68 (160)
Baclofen 0.63 to 2.5 > 2.5 - > 2.5 3.1 ± 1.3 (2.5) > 2.5 - 2.5 2.6 ± 1.3 (2.5)
Carbamazepine 40 > 40 - > 40 5.7 ± 1.1 (40) < 40 - > 40 5 ± 1.4 (40)
Ketamine 10 to 40 22 a
ND 40 0.57 ± 0.57 (40) 22 a
ND 40 1.6 ± 1.0 (40)
Sumatriptan
40 > 40 - 40 5.7 ± 0.64 (40) > 40 - 40 6.5 ± 0.3 (40)
ABT-594 0.01 to 0.16 0.033 0.012 to 0.092 0.16 0.57 ± 0.57 (0.16) 0.013 0.0021 to 0.086 0.16 1.4 ± 1.4 (0.16)
F-13640 0.01 to 2.5 0.081 0.051 to 0.13 0.16 0 ± 0 (0.16) 0.081 0.051 to 0.13 0.16 0 ± 0 (0.16)
All compounds were injected intraperitoneally 15 min before formalin injection. ED50 values, confidence limits (CL) and all drug doses are in mg/kg. The maximal drug effect is represented by the
lowest mean (± SEM) score found with any dose (dose between brackets). a the ED50 was not calculated but was found by linear interpolation. MSD minimal significant dose, ND not determined
because of insufficient data.
42 Current Opinion in Investigational Drugs 2006 Vol 7 No 1

5-HT1A receptor activation Colpaert 43
Table 2. Quantification of the ability of various analgesic agents to inhibit formalin-induced paw elevation during the early and late phases following intraplantar formalin injection in
rats.
Drug Dose range Inhibition of formalin-induced paw elevation
Early phase Late phase
ED50 95% CL MSD Lowest mean score ED50 95% CL MSD Lowest mean score
Morphine 1.25 to 40 4.2 2.2 to 7.8 10 3.1 ± 1.2 (40) 2.1 1.1 to 3.7 10 0 ± 0 (10)
Buprenorphine 0.01 to 10 > 10 - > 10 9.1 ± 0.7 (10) 5.8 0.51 to 70 0.63 5.4 ± 1.9 (0.63)
Imipramine 2.5 to 40 14 3.9 to 48 40 3.4 ± 1.3 (40) 7.2 2.8 to 19 10 0 ± 0 (40)
Amitryptyline 2.5 to 40 18 9.2 to 36 40 0 ± 0 (40) 18 9.2 to 36 40 0 ± 0 (40)
Paroxetine 2.5 to 40 > 40 - > 40 9.3 ± 0.47 (40) 16 6.1 to 41 40 2.7 ± 1.8 (40)
Aspirin 160 > 160 - > 160 8.8 ± 0.55 (160) > 160 - > 160 9.8 ± 0.14 (160)
Diclofenac 40 to 160 > 160 - 160 4.1 ± 0.77 (160) > 160 - 160 0.43 ± 0.43 (160)
Paracetamol 10 to 160 > 160 - > 160 9.7 ± 0.29 (160) 55 16 to 192 160 5.2 ± 1.5 (160)
Rofecoxib 40 to 160 > 160 - > 160 9.6 ± 0.2 (160) > 160 - > 160 9.4 ± 0.43 (40)
Celecoxib 40 to 160 > 160 - > 160 9.7 ± 0.18 (160) > 160 - > 160 10 ± 0 (160)
Gabapentin 10 to 640 > 640 - > 640 9.5 ± 0.3 (40) > 640 - > 640 8.5 ± 1.2 (160)
Baclofen 0.63 to 2.5 > 2.5 - > 2.5 7 ± 1.6 (2.5) > 2.5 - 2.5 4.3 ± 1.4 (2.5)
Carbamazepine 40 > 40 - > 40 10 ± 0 (40) > 40 - > 40 10 ± 0 (40)
Ketamine 10 to 40 > 40 - > 40 9.7 ± 0.29 (40) > 40 - 40 5.7 ± 2 (40)
Sumatriptan 40 > 40 - > 40 9.7 ± 0.29 (40) > 40 - > 40 10 ± 0 (40)
ABT-594 0.01 to 0.16 0.041 0.014 to 0.12 0.16 1.4 ± 1.4 (0.16) 0.068 0.027 to 0.18 0.16 1.4 ± 1.4 (0.16)
F-13640 0.01 to 2.5 0.029 0.0075 to 0.11 0.16 0 ± 0 (0.63) 0.081 0.051 to 0.13 0.16 0 ± 0 (0.16)
All compounds were injected intraperitoneally 15 min before formalin injection. ED50 values, confidence limits (CL) and all drug doses are in mg/kg. The maximal drug effect is represented by the
lowest mean (± SEM) score found with any dose (dose between brackets). MSD minimal significant dose.
Table 3. Comparative data on the effects of F-13640 and four other centrally acting analgesics in rat models of chronic nociceptive or neuropathic pain.
Parameter (unit) Treatment (mg/rat/day)
Vehicle
Morphine
Ketamine
Imipramine Gabapentin (10) F-13640
(0)
Chronic nociceptive pain (adjuvant arthritis)
(5)
(20)
(2.5)
(0.63)
FSA (g) 60 (40 to 72) 42* (21 to 63) 52 (34 to 88) 47* (18 to 51) 49 (36 to 70) 35** (20 to 54)
Chronic neuropathic pain (spinal cord injury)
Response to brush (score) 2.2 (0.07) 2.7 (0.07) 2.5 (0.09) 2.3 (0.12) 2.2 (0.10) 1.0*** (0.11)
Response to cold (score) 2.7 (0.05) 2.8 (0.07) 2.7 (0.07) 2.8 (0.05) 2.5 (0.07) 2.0** (0.09)
von Frey threshold (g) 1.4 (0.05) 3.7 (0.04) 4.3 (0.03) 3.9 (0.04) 4.6 (0.05) 5.7* (0.07)
Chronic neuropathic pain (sciatic nerve constriction)
von Frey threshold (g) 17 (0.89) 20 (1.30) 20 (3.80) 22 (3.80) 23* (4.40) 24** (2.30)
Data are based on observations that were made during 2 weeks after the subcutaneous implantation of osmotic minipumps that infused vehicle or agents at a constant rate. Doses (expressed in
mg/rat/day) for the four reference analgesics correspond to the highest dose (concentration) that could be administered in the experimental conditions. Results are expressed as the median (and
inter-quartile range for fentanyl self administered; FSA) or the mean (+SEM for other parameters). (*p < 0.05; **p < 0.01; ***p < 0.001).
5-HT1A receptor activation Colpaert 43

44 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
both an intensity- and duration-dependent manner [10•]. Thus,
the sustained, intense nociception associated with adjuvant
arthritis may have sufficiently inhibited opioid analgesia
tolerance development for morphine analgesia to have
remained significant, at least over the 2-week period. Agents
exemplifying other central mechanisms of analgesia (eg, the 5-
HT and noradrenaline re-uptake inhibitor imipramine (2.5
mg/day), the excitatory amino acid antagonist ketamine (20
mg/day), and the anticonvulsant gabapentin (10 mg/day))
were inactive (Table 3). Similar to tonic nociceptive pain, the
data suggest that high-efficacy 5-HT1A receptor activation
produces an analgesia with chronic nociceptive pain that is
rivaled only, if at all, by morphine-like opioids.
Chronic neuropathic pain
In a model of peripheral neuropathic pain, rats undergo a
unilateral chronic constriction injury of the common sciatic
nerve and demonstrate a lowered threshold for von Frey
filament stimulation to induce paw withdrawal [33]. A 2-week
infusion of morphine, ketamine or imipramine produced a
slight, non-significant increase of the ipsilateral reduced
threshold in saline-treated rats (17 g), while gabapentin exerted
a significant effect (Table 3). F-13640 produced a larger, highly
significant increase, suggesting robust efficacy in this model
[15•]. This effect on ipsilateral threshold was behaviorally
specific, in that F-13640 did not modify the contralateral
threshold in saline-treated rats (69 g).
In a model of central neuropathic pain, rats received a
photochemical, ischemic injury of spinal cord dorsal segments
L3 to L5 and developed allodynic responses to cutaneous
stimulations such as von Frey filament application, a gentle
brush or a cold spray [34]. Interestingly, and as with sciatic
nerve constriction, subcutaneously infused morphine,
ketamine, imipramine and gabapentin increased the von Frey
threshold to some extent, although not significantly so; these
agents also exerted no significant effect in response to a gentle
brush or a cold spray (Table 3). In contrast, F-13640 robustly
inhibited all three responses [15•]. The effects of F-13640 grew
in the course of the 2-week treatment period, demonstrating
inverse analgesic tolerance.
The acute injection of F-13640, as well as that of morphine,
can counteract allodynic responses to von Frey filament
stimulation in rats sustaining a chronic constriction injury of
the infra-orbital nerve (IoN-CCI), a model of trigeminal
neuropathic pain [35]. The effects of F-13640 in this model
are again behaviorally specific [36]. In these rats, morphine
infusion initially produces a robust, significant analgesia to
which complete tolerance develops after 2 weeks; the effects
of F-13640 increased rather than declined during the 2-week
period, again demonstrating inverse tolerance [37•,38,39,40•].
Collectively, these data suggest that high-efficacy 5-HT1A
receptor activation may produce exceptionally powerful and
sustained, 'symptomatic' analgesia with chronic neuropathic
pain of peripheral or central origin.
Pre-emptive and curative-like analgesia
Much as opioids induce a hyperalgesia and tolerance that
may outlast µ-opioid receptor activation for a long time (eg,
a year [10•,41]), the signal-transduction concept suggests
that a neuropharmacological manipulation that generates
the inverse of opioid actions should induce analgesia (and
continue to demonstrate inverse tolerance) long after its
implementation has been discontinued.
Rats were infused with 0.63 mg/day of F-13640 for 8 weeks
starting 24 h before the spinal cord injury described
previously; with all three cutaneous stimulations the
treatment effect persisted unabated for 2 months following
discontinuation of treatment [42]. These data, together with
the consideration that F-13640 is effective in neuropathic
pain regardless of its peripheral or central origin, suggest
that high-efficacy 5-HT1A receptor activation may
powerfully 'pre-empt' pain ensuing from neuronal damage,
such as that resulting from surgical nerve injury or diabetes.
To explore this suggestion, rats having sustained spinal cord
injury and having fully developed allodynia were then
infused with F-13640 (0.63 mg/day) for 56 days. The
treatment increasingly alleviated and eventually normalized
the allodynic responses, thereby demonstrating inverse
tolerance. More importantly, during the 70-day period that
ensued, the effects of F-13640 persisted, demonstrating an
unprecedented 'curative-like' action on allodynic pain [40•].
It remains to be determined whether these pre-emptive and
curative-like actions are mediated by the neuron-protective
and astroglial reaction-inhibitory effects that 5-HT1A
agonists may produce in ischemic brain tissue [43].
Although it might be of interest to similarly examine the
potential pre-emptive and curative-like actions of morphine,
ketamine, imipramine and gabapentin, the absence of
significant symptomatic effects with these agents in the
spinal cord injury model has prevented the research group
from doing so. Indeed, any such pre-emptive actions
reported so far have concerned pain parameters that
respond in a symptomatic manner to the agents being
considered [44,45]. Prominent among these agents are
opioids, and the largest symptomatic effects observed to
date with continuous, 2-week infusion of any comparable
analgesic in any model of neuropathic pain were obtained
with 5 mg/day of morphine in the IoN-CCI model [37•,38].
As indicated, soon after the initiation of morphine infusion,
a robust analgesia occurs in this model, to which tolerance
develops within 2 weeks. At that stage, discontinuation of
morphine infusion does not afford analgesia, and in fact
causes hyperallodynia [53].
Tolerability
Although the data discussed previously allow assessment of
the comparative therapeutic potential of F-13640 relative to
currently available treatments to a considerable extent, the
evidence available so far offers only little in the way of an
evaluation of the relative tolerability of the compound.
Regarding the opioids, however, one issue stands out; it is
now recognized that the chronic use of opioids induces an
analgesic tolerance that not only limits, or dissipates their
therapeutic usefulness, but is also accompanied by
hyperalgesia and opioid-induced pain [10•,13,14]. In
addition to the well-known side effects of opioids, this druginduced
pain may become 'excruciating', thus severely

compromising the tolerability of opioids; indeed, the
discontinuation of opioid treatment in these conditions may
act to alleviate pain [46]. The preclinical data discussed
suggest that, in contrast, chronic administration of F-13640
produces an analgesia that grows rather than decays. Of
particular concern, is that agents that interact with
serotonergic neurotransmission (eg, 5-HT re-uptake
inhibitors and opioids) may induce 'serotonin syndrome' in
humans [47]. In several animal species, 5-HT1A agonists,
including F-13640, induce behavioral effects such as the
retraction of the lower lip and postural movements in rats,
forepaw treading, splayed hindlimbs, flat body posture and
locomotion [48-50]. Among the agents that induce at least
some of those signs in rats are antidepressant uptake
inhibitors of 5-HT and noradrenaline and buspirone [49,51],
yet while the occurrence of serotonin syndrome is
sporadically reported with several 5-HT and noradrenaline
uptake inhibitors and opioids [47], no such occurrence has
been observed with buspirone, in spite of the considerable
evidence of the syndrome that has now accumulated with
regard to this agent in humans. However, no clinical data
are currently available regarding selective, higher-efficacy
5-HT1A agonists such as F-13640.
Clearly, however, with repeated or continuous administration,
the analgesic action of F-13640 grows, while at the same time
tachyphylaxis develops to the ability of the drug to induce
behavioral and other signs, for example, hypothermia
[15•,37•,38,39,40•,42], indicating that, in the rat, the
tolerability of 5-HT1A agonists increases considerably in
conditions of chronic drug administration.
Neurobiology of hyper- and hypoalgesia
The evidence discussed in this review is consistent with
recent data indicating that both 5-HT1A and µ-opioid
receptor agonists produce apparently complex, paradoxical
hypo- and hyperalgesic actions (see references [10•,11-14]
for reviews). To a considerable extent, this apparent
complexity is likely resolved by taking into account the
'base-line' stimulation to which pain-processing systems are
exposed. Thus, both 5-HT1A receptor-mediated and opioid
hyperalgesia are counteracted in a duration- and intensitydependent
manner by nociceptive stimulation, which
enhances the analgesia produced by both 5-HT1A and opioid
receptor agonists [10•]. Thus, while 5-HT1A agonists may
counteract opioid hypoalgesia in animals that are exposed to
limited nociceptive stimulation [52], F-13640 counteracts the
hyper-allodynia that develops following long-term opioid
treatment in IoN-CCI-lesioned, chronically allodynic rats
[53].
The 5-HT1A receptor, like µ-opioid receptors, is an inhibitory
G-protein-coupled receptor. It is located with high density
post-synaptically to 5-HT neurons in the hippocampus and
neocortex and, as a pre-synaptic autoreceptor, in the raphe
nuclei from where projections descend to pain-processing
neurons in the spinal cord dorsal horn where 5-HT1A
receptors are located post-synaptically [2,54]. Marked
regional differences in the functional adaptation of 5-HT1A
receptors occur after long-term stimulation; chronic
exposure to direct or indirect (ie, 5-HT uptake inhibitors)
5-HT1A receptor activation Colpaert 45
agonists desensitizes 5-HT1A presynaptic autoreceptors in
the raphe nuclei without altering the response properties of
post-synaptic 5-HT1A receptors in the projection areas (eg,
the spinal cord dorsal horn) of raphe neurons [55]. Thus,
with chronic exposure, the 5-HT1A autoreceptor-mediated
inhibitory feedback control of serotonergic neurotransmission
decays, enabling serotonergic signaling at post-synaptic
5-HT1A receptors [55]. This desensitization of presynaptic
5-HT1A autoreceptors may conceivably play a role in the
tachyphylaxis that develops to 5-HT1A agonist-induced
hyperalgesia, but further research is required to elucidate
this point.
Conclusions
The preclinical evidence summarized here suggests that
high-efficacy 5-HT1A receptor stimulation presents a new
molecular and neuroadaptive approach to the treatment of
acute and chronic, nociceptive and neuropathic pain states,
as well as achieving pain relief in conditions that have
remained inaccessible, even after opioid or other treatment.
Having never been studied in humans, clinical
investigations are now in order to assess the efficacy of
compounds such as F-13640 in patients.
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48
Glycine receptors: A new therapeutic target in pain pathways
Joseph W Lynch 1 * & Robert J Callister 2
Addresses
1 School of Biomedical Sciences
University of Queensland
Brisbane
QLD 4072
Australia
Email: j.lynch@uq.edu.au
2School of Biomedical Sciences
Faculty of Health and Hunter Medical Research Institute
University of Newcastle
Callaghan
NSW 2308
Australia
*To whom correspondence should be addressed
Current Opinion in Investigational Drugs 2006 7(1):48-53
© The Thomson Corporation ISSN 1472-4472
Although glycine receptor Cl − channels (GlyRs) have long been
known to mediate inhibitory neurotransmission onto spinal
nociceptive neurons, their therapeutic potential for peripheral
analgesia has received little attention. However, it has been shown
that α3-subunit-containing GlyRs are concentrated into regions of
the spinal cord dorsal horn where nociceptive afferents terminate.
Furthermore, inflammatory mediators specifically inhibit α3containing
GlyRs, and deletion of the murine α3 gene confers
insensitivity to chronic inflammatory pain. This strongly
implicates GlyRs in the inflammation-mediated disinhibition of
centrally projecting nociceptive neurons. Future therapies aimed
at specifically increasing current flux through α3-containing
GlyRs may prove effective in providing analgesia.
Keywords Analgesia, chloride channel, drug discovery,
inflammatory pain, inhibitory neurotransmission,
neuropathic pain, spinal cord
Introduction
Pain is a complex and highly modifiable sensory experience.
Over the past 50 years our view of pain mechanisms and
treatment has changed considerably. The current paradigm
is that pain results from the complex interaction of a variety
of synaptic inputs in a pathway that begins at peripheral
receptors, ascends the neural axis, and finally reaches the
cerebral cortex and limbic structures, such as the amygdala
[1•]. The majority of current approaches to treating pain are
based on the idea that increasing the level of inhibitory drive
or tone at key central nervous system (CNS) regions in the
pain pathway can alter pain perception [2-4,5•]. Because
γ-aminobutyric acid (GABA)A and glycine receptor Cl −
channels (GABAARs and GlyRs) mediate inhibitory
neurotransmission in the CNS, they represent key targets for
pharmacologically manipulating inhibitory drive.
Until recently, investigation of inhibitory mechanisms in
pain processing focused on the role of GABAARs in various
regions of the pain pathway, particularly in the dorsal horn
of the spinal cord and in the brainstem [2,3,5•,6]. The role of
GlyRs in pain processing has largely been ignored because
of the lack of pharmaceutical agents that specifically
modulate them in a therapeutically useful way. However, this
situation has changed with the demonstration that α3 subunitcontaining
GlyRs expressed in spinal cord dorsal horn synapses
are specifically inhibited by inflammatory mediators [7••].
These GlyRs, which are sparsely expressed outside the spinal
cord dorsal horn, represent a new analgesic target. Molecules
that can specifically enhance (or potentiate) Cl − current flow
through this particular GlyR isoform offer promise as
therapeutic lead compounds. The challenge now is to identify
such molecules. This review summarizes our current
understanding of GlyRs in terms of their distribution in regions
of the CNS important in pain processing, their subunit
composition, and mechanisms by which they may be
modulated.
The ascending pain pathway
Although there is much conjecture and disagreement regarding
the specific details of ascending pain pathways [1•,8-11], any
approach to the treatment of painful conditions requires an
understanding of the elements and circuitry of the pathway.
The classic pain-processing pathway involves numerous
neuron clusters (hereafter termed 'nodes') located in
anatomically discrete regions of the CNS (Figure 1A). The
nodes, especially those in the spinal cord and brainstem, are
known to contain sub-synaptic GlyRs and GABAARs that
participate in Cl − -mediated fast inhibitory synaptic
transmission [12,13,14•,15-17]. Immunohistochemical and
electrophysiological studies have also shown that cortical and
sub-cortical centers contain extra-synaptic GlyRs (for examples,
see below). Because these extra-synaptic receptors are located in
brain regions known to be important in pain processing, the
specific targeting of extra-synaptic GlyRs may, in principal,
offer a therapeutic route for the treatment of pain. However, as
the role of non-synaptic GlyRs in brain function is not yet
understood, we focus on synaptic GlyRs as potential targets for
pain therapies.
Nociceptors located in the skin, deep tissues and viscera signal
the presence of potentially harmful (or noxious) stimuli (Figure
1B and C) [1•]. Central projections from these peripheral
receptors enter the spinal cord dorsal horn via small-diameter
(Aδ- and C-fiber) primary afferents [18•,19•]. Other sensory
receptors also provide signals to the dorsal horn regarding nonnoxious
stimuli in both cutaneous and deep tissues, via largediameter,
myelinated Aβ fibers [1•]. Inputs from both small-
and large-diameter afferents make synaptic connections with
various neuronal types in specific stratified zones (or laminae)
of the dorsal horn (Figure 1C). Neurons in laminae I and II (the
outermost strata) receive both monosynaptic and polysynaptic
input from Aδ- and C-fibers. Neurons in laminae III to IV
receive input almost exclusively from large-diameter Aβ-fibers,
and neurons in lamina V receive input from Aδ-, C- and Aβfibers.
Projection neurons in laminae I and V relay this
information onto ascending pain pathways [8].
Classic textbook views of dorsal horn circuitry overly focus
on projection neurons because they are the output neurons
of the dorsal horn, contribute to ascending pathways, and

Figure 1. Important components of the pain pathway.
A
Cortex
Thalamus
PAG, LC
PB
RVM
DH
B
C
Glycine receptors Lynch & Callister 49
(A) Key processing nodes in the pain pathway. Spike trains carrying information regarding noxious and innocuous stimuli are processed in
the dorsal horn (DH) of the spinal cord and further processed in various nodes (ellipses) as they ascend the neural axis to eventually reach
the thalamus and cortical regions. Midbrain nodes, such as the periaqueductal gray (PAG), locus coeruleus (LC), and para-brachial nucleus
(PB), exert powerful descending modulatory effects on the DH via their projections to another pain node, the rostral ventromedial medulla
(RVM spinal projection: thick arrow). (B) Spinal cord cross-section showing peripheral sensory afferents entering the DH, the first processing
node in the pain pathway. Projection neurons (black stars) provide the output of the dorsal horn and are located in laminae I and V. (C)
Expanded view (region circled in B) of the DH emphasising the role of excitatory (gray circles) and inhibitory (white circles) interneurons in
DH circuitry. In the superficial strata (laminae I and II) of the DH, Aδ- and C-fibers contact projection neurons (black stars) as well as
excitatory and inhibitory interneurons. These interneurons contact other interneurons and also receive input from descending pathways (not
shown; see Figure 1A). Neurons in deeper laminae (IV to VI) receive input from Aδ- and C-fibers in addition to large-diameter Aβ-fibers. In
some chronic pain states, it is believed that spinal cord circuits are altered so that the influence of large-diameter afferents on the excitability
of projection neurons increases. Numerous studies have shown that reduced inhibition in DH circuits plays a key role, however, the exact
circuitry and mechanisms are unknown.
provide different qualities to pain perception [8,20].
However, it must be emphasized that the neuron population
of the dorsal horn is highly heterogeneous. Most neurons
are, in fact, excitatory or inhibitory interneurons [21••,22].
The inhibitory interneurons can be broadly grouped into
those that express GABAARs and those that express both
GABAARs and GlyRs [12,13]. Importantly, their activity can
dramatically alter the excitability of projection neurons
[14•,21••,22-25]. Thus, understanding inhibitory interneuron
function is central to pain mechanisms, pain perception and
pain therapy (Figure 1C).
Descending pathways
A major principle of sensory system neurobiology is that the
CNS itself exerts powerful control over the flow of
information from peripheral receptors [2,3,8]. The first
experimental evidence for such an 'endogenous pain control
mechanism' came in the late 1960s, when it was reported
that stimulation of the midbrain periaqueductal gray (PAG)
reduced responses to painful stimuli in rats [26]. Subsequent
studies have reported that stimulation of analogous brain
regions in humans can produce analgesia in patients
suffering from intractable cancer pain [27]. Accordingly,
there has been considerable clinical interest in this
mechanism [28]. Indeed, opiate administration, currently a
major therapeutic approach to the treatment of both acute
C
Aδ
Aβ
and chronic pain, relies on the recruitment of endogenous
(inhibitory) pain control mechanisms [29,30].
The importance of descending pathways in blunting or
inhibiting responses to painful stimuli is now well accepted
[2,6,29]. Unfortunately, some studies in animal models of
chronic pain have shown that activation of descending
pathways can also enhance pain responses [31,32]. Thus, the
role of descending inputs is more complex than previously
thought and this could help explain why the treatment of
chronic pain has been so problematic.
Several brainstem nuclei are well recognized as midbrain
pain processing nodes (Figure 1A). These include the PAG,
the locus coeruleus (LC), the parabrachial nucleus (PB) and
the rostral ventromedial medulla (RVM) [2,3]. Although
these regions contain GlyRs [33,34••,35-37], the exact
circuitry and synaptic linkages involved are extremely
complex and are poorly understood. The available
electrophysiological, anatomical and behavioral data suggest
that the more rostral nuclei exert their modulatory effects on
spinal cord processing via relays to the RVM (Figure 1A).
RVM inputs arrive at all cell types in the dorsal horn of the
spinal cord [19•,34••,38]; however, little is known about
specific descending connections with glycinergic
interneurons.

50 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Inhibitory mechanisms in the spinal cord and
the gate theory of pain
In 1965, Melzack and Wall proposed the 'gate control' theory
of pain [39••]. At the time there was great interest in
descending inhibitory pathways and their capacity to inhibit
spinal reflexes [40]. Simplistically, this theory stated that
inhibitory synaptic mechanisms in the spinal cord dorsal
horn play a key role in determining whether peripheral
stimuli on small-diameter afferent fibers (Aδ- and C-fibers)
can raise the level of excitability in projection neurons and
subsequently be perceived as painful. Even though the
original theory has been criticized, its influence has persisted
because it emphasized the importance of inhibitory
mechanisms.
Under normal conditions, inhibitory drive in spinal
projection and local circuit neurons is mediated by both
GABAAergic and glycinergic synapses [5•,14•,25,34••,35,41].
Although the exact contribution of these two forms of
inhibition is unknown, the faster kinetics of glycinergic
inhibitory post-synaptic currents implies that they have
distinct roles in synaptic integration [12,13,42]. It is also
important to note that these receptors may cease to be
inhibitory in neuropathic pain; an increase in intracellular
Cl − in lamina I neurons following peripheral nerve injury
results in depolarization and action potential generation
following GABAAR activation [43].
Following both peripheral inflammation and nerve injury,
there is an extensive physiological and morphological
reorganization in dorsal horn circuitry, which ultimately
leads to a net reduction in inhibitory tone [5•,44•,45-48] and
increased excitability in ascending pathways. Likewise,
descending inhibitory mechanisms acting via pre- and postsynaptic
mechanisms are known to be important in setting
excitability levels in both normal and pathological
conditions [1•,2,8].
GlyR subunit composition and distribution
GlyRs belong to the cysteine-loop family of ligand-gated ion
channel receptors. A total of five GlyR subunits (α1 to α4
and β) plus several splice variants have been identified [49•].
Functional receptors comprise either α homomeric
pentamers or α:β heteromers in a 2:3 stoichiometry [50••].
The cytoplasmic protein gephyrin binds only to the βsubunit
and is essential for clustering GlyRs at post-synaptic
densities [51].
Homomeric α2 GlyRs are abundantly and evenly distributed
over the membrane surface of embryonic neurons [52].
Because intracellular Cl − concentration is high, activation of
embryonic GlyRs induces neuronal depolarization and a
subsequent calcium influx that is important for neuronal
differentiation [53,54]. Glycinergic synapses begin to form
before birth in the rat, with their appearance correlating with
the expression of the β-subunit [55]. By the third postnatal
week, most α2 homomers have been replaced by α1β
heteromers [52]. This isoform predominates at spinal cord
inhibitory synapses and also mediates inhibitory
neurotransmission in several brainstem nuclei, as well as at
defined synapses in the cerebellum and retina [49•]. The α2
and α3 subunits are expressed at lower levels in the adult
and exhibit distinct synaptic expression patterns that are
particularly evident in the retina [56,57•]. The α3 subunit is
also incorporated into GlyRs on neurons in lamina II of the
dorsal horn [7••]. The α4 subunit is a pseudo-gene in
humans [58].
Non-synaptic GlyRs are more widely distributed throughout
the adult nervous system. They have so far been found in
the cortex [53], dorsal midbrain [59••], hippocampus [60],
caudatoputamen [61] and basolateral amygdala [62]. As
stated previously, little is known about their roles. However,
one study, published in 2005, demonstrated that α3 subunit
transcripts undergo RNA editing, resulting in a P185L
substitution in the external ligand-binding domain [59••].
This mutation dramatically increases glycine sensitivity,
with the result that non-synaptic α3-containing GlyRs in the
superior colliculus are held open by ambient glycine,
resulting in strong tonic inhibition [59••]. The amount of
mutant transcript in immature brain is increased by brain
slicing, suggesting that the RNA editing process may be an
adaptive mechanism to compensate for excessive
excitability. Many questions remain about this mechanism.
For example, its anatomical distribution and subunitspecificity
are not known, and the extent to which it occurs
in vivo under physiological or realistic pathological
(including pain) conditions also remains to be elucidated.
GlyR α3 subunits and pain
Although GlyR α3 subunits are sparsely distributed, some
research has identified a specific role for them in spinal cord
pain processing. First it was shown that the inflammatory
mediator prostaglandin E2 (PGE2) reduced inhibitory
glycinergic neurotransmission onto lamina II neurons [63••].
This effect, mediated via activation of the EP2 receptor,
involved the activation of a cholera-toxin-sensitive G protein
and a cAMP-dependent protein kinase. This important
finding implied that inflammatory pain sensitization is
mediated, at least in part, by an inhibition of spinal
glycinergic neurotransmission.
A subsequent study demonstrated that α1 and α3 subunits
were equally represented at glycinergic synapses in lamina
II neurons [7••]. Recombinantly expressed α3 GlyRs were
inhibited by PGE2 via a protein kinase (PK)A-dependent
phosphorylation [7••]. However, α1 GlyRs, which do not
have PKA-dependent phosphorylation sites, were not
affected. This prompted the hypothesis that the α3 subunit
was specifically modulated by inflammatory stimuli. A GlyR
α3 knockout mouse was used to test this theory further.
Although the mice displayed no overt behavioral
phenotype, the PGE2-dependent decrease of lamina II
glycinergic currents was abolished [7••]. Behaviorally,
normal and GlyR α3 -/- mice responded similarly to acute
pain stimuli. However, peripheral inflammation produced
pain sensitization in normal animals, but not in the GlyR α3
-/- animals [7••]. These findings show that the currents
carried by α3-containing GlyRs are specifically inhibited in
an animal model of inflammatory pain. Such an effect would

educe the inhibitory drive onto nociceptive projection
neurons, thereby increasing the transmission of nociceptive
stimuli to the brain.
The GlyR α3 subunit as a therapeutic target
In principal, there are several ways to compensate for the
effects of inflammation on α3-containing GlyRs. One is to
increase the magnitude or slow the decay rate of glycinergic
synaptic currents in lamina II neurons (Figure 1C), and
another is to increase the magnitude of non-synaptic GlyRs
(or other Cl − channels) in these neurons. Although
increasing the current through α1-containing GlyRs should
compensate for the decrease in current through α3containing
GlyRs, the risk of side effects is higher given that
α1 subunits are more widespread outside lamina II. Ideally,
therapeutic interventions should selectively increase current
through the downregulated (ie, phosphorylated) α3containing
GlyRs.
Unfortunately, very little is known about the pharmacology of
α3-containing GlyRs. Until publication of the study by Harvey
et al [7••], this subunit was virtually ignored because of its low
expression and limited distribution. The physiology and
molecular pharmacology of α1, α2, α1β and α2β GlyRs have
been studied in much more detail, and several classes of
compounds (eg, tropeines, alcohols and volatile anesthetics,
butyrolactones, neurosteroids and dihydropyridines) are
known to potentiate these receptors in a subunit-specific
manner [49•]. These compound families may provide a starting
point for identifying α3-specific potentiating agents.
An alternative therapeutic approach might involve interfering
with post-translational modifications that affect the magnitude
or sensitivity of glycinergic currents. One potential mechanism
involves the previously described RNA editing process that
leads to the α3 subunit P185L mutation. If the glycine sensitivity
of spinal α3 GlyRs could be increased via this mechanism, the
resulting enhanced inhibition may effect some degree of relief
from chronic pain syndromes.
Conclusion
Pain-processing circuitry increases in complexity as it
ascends the neural axis. A great deal is now known
regarding the neuronal types and distribution of GlyR
subunits in spinal cord pain-processing circuits, but rather
less is known about their role in higher brain regions. Thus,
the spinal cord dorsal horn would appear to be the best
place to focus efforts on using GlyR modulation to alter pain
processing. As spinal GlyR α3 subunits are specifically
inhibited by inflammatory mediators in an animal model of
chronic pain, this receptor provides an excellent candidate
therapeutic target.
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54
Does VEGF represent a potential treatment for amyotrophic lateral
sclerosis?
Joanna Iłżecka
Address
Department of Neurology
Medical University
Jaczewskiego 8
20-954 Lublin
Poland
Email: ilzecka@onet.pl
Current Opinion in Investigational Drugs 2006 7(1):54-59
© The Thomson Corporation ISSN 1472-4472
Amyotrophic lateral sclerosis (ALS) is a progressive
neurodegenerative disease. The pathogenesis of ALS is unclear
and there is no effective treatment. Vascular endothelial growth
factor (VEGF) is a cytokine that has a protective function via
angiogenic, neurotrophic, gliotrophic and anti-apoptotic
activity. Data indicate that VEGF can inhibit neurodegeneration
in ALS and may have therapeutic potential in this disease. The
use of gene therapy to deliver VEGF into the central nervous
system is being evaluated.
Keywords Amyotrophic lateral sclerosis, neurodegeneration,
neuroprotection, therapy, vascular endothelial growth factor
Introduction
Amyotrophic lateral sclerosis (ALS) is a progressive
neurodegenerative disease affecting motor neurons in the
spinal cord, brain stem and motor cortex. The pathogenesis
of ALS is still obscure, but there is evidence that oxidative
stress, glutamate-induced toxicity and withdrawal of trophic
factors may play an important role [1]. It was previously
revealed that mutations in the superoxide dismutase
(SOD)1 gene are implicated in pathogenesis of familial ALS
[2] and investigations have shown that apoptosis appears to
be the primary mechanism of cell death in this disease. In
the past few years, attention has been paid to the potential
role of vascular endothelial growth factor (VEGF) in the
pathogenesis of ALS. Data from the literature indicate that
VEGF can play a protective and reparative function in the
central nervous system (CNS) via angiogenic, neurotrophic,
gliotrophic and anti-apoptotic activity.
VEGF is a glycoprotein acting via receptors VEGFR1 (Flt-1),
VEGFR2 (KDR/Flk-1), VEGFR3 (Flt-4) and neuropilin-1 and
-2 [3,4]. Spliet et al demonstrated an altered expression of
VEGFRs in human spinal cord in ALS, indicating their
significant role in spinal cord pathology [5]. VEGF-1
expression is increased in reactive astroglial cells and in the
blood vessels of ALS spinal cord. The higher expression of
VEGFR2 in blood vessels of spinal cord and lower
expression of VEGF-3 in neuropil was also observed.
The interactions between neuronal, astrocytic and
endothelial cells are important for metabolic brain functions.
Blood vessels can modulate the activity of neurons and the
influence of neurons on blood vessel function. The vascular
tone of the blood vessels is regulated through excitatory
signal transmissions, and astrocytes play a critically
important role in this process. It is known that VEGF is a
major regulator of angiogenesis, and both angiogenesis and
neurogenesis are regulated by systemic coordinations.
Neuroangiogenic factors, including VEGF, influence the
proliferation and differentiation of neuronal and endothelial
cells [6]. This growth factor induces endothelial regeneration
and influences nitric oxide and prostacyclin production,
resulting in vasodilatation, inhibition of vascular smoothmuscle
cell proliferation and aggregation of platelets [7,8].
VEGF influences vascularization and reduces retrograde
degeneration of transected corticospinal tract axons [9]. It
can promote collateral vessel growth in animal models of
ischemia [10]. VEGF can also protect regression of vasa
nervorum, which improves the function of peripheral nerves
[11]. A previous study revealed that local production of
VEGF by microvessels supports the survival and
regeneration of motor nerves [12].
VEGF and neuroprotection
Previous data have shown that VEGF may influence
neuronal and glial cells [13], and it was demonstrated that
VEGF expressed by neurons can serve both paracrine and
autocrine functions in the CNS [14]. Studies have shown that
VEGF and its receptors, localized on neurons and astrocytes,
play a neuroprotective role against ischemia and spinal cord
injury. The functions of vascular and nervous tissue are
linked because VEGF shares common receptor signaling
with SEMA3A [15].
According to Sun and Guo, the mechanisms by which VEGF
exerts neuroprotection include the modulation of the
phosphatidylinositol 3'-kinase (PI3K)/Akt/nuclear factor
(NF)κB signaling pathway, induction of neural progenitor
proliferation, activation of neuron maturation in adult rat
brain and inhibition of apoptosis [16]. However, these
neuroprotective mechanisms have not been confirmed in
human studies and it is difficult to assess the molecular
activity of VEGF in ALS patients. Thus far, it is still
uncertain whether apoptosis plays a role in cell death in
ALS, or if the inhibition of apoptosis by VEGF has a
protective effect in this disease. Studies have demonstrated
that VEGF is a mitogen for astrocytes [17], and VEGF has
been shown to stimulate neurogenesis in the proliferative
zones of the human brain [18]. VEGF also has a neurotrophic
effect, via induction of motor neurons that confer protection
against hypoxia [19•], and can reduce the hypoxic death of
cultured cerebral cortical neurons via activation of VEGFR2
[20]. In endothelial cells, VEGF attenuates oxidative injury
through inhibition of reactive species production and by
induction of SOD2 expression [21,22]. It was also observed
that VEGF has a neuroprotective effect on hippocampal
neurons [23,24]. Another investigation showed that the
inactivation of VEGF in the nervous system leads to
diminishing vessel density, resulting in ischemia and severe
degeneration [25]. It is also known that manganese
superoxide dismutase (Mn-SOD) plays a protective role

against oxidative stress injury. VEGF can stimulate
expression of Mn-SOD through the negative PI3K/Aktforkhead
pathway and the positive protein kinase C-NFκB
pathway [26]. VEGFR and Akt offer protection in
experimental models of hypoxic cerebellar granule neurons
[27], and VEGF also protects motor neurons against
glutamate and N-methyl-D-aspartate toxicity. VEGF inhibits
glutamate-mediated toxicity through PI3K/Akt and
MEK/ERK anti-apoptotic pathways [28••], and it has also
been revealed that VEGF plays an important role in the
growth and structural stability of neurons [29]. A protective
effect was observed in hippocampal, cortical, cerebellar,
dopaminergic and other neurons, along with a
neuroprotective role in cerebral ischemic stroke [30,31],
offering protection via enhancing angiogenesis in the
penumbra and reducing infarct volume [32,33]. Previous
studies demonstrated that VEGF influences apoptosis,
exerting anti-apoptotic activity through inhibition of
caspase-3 pathways and via VEGFR2-mediated activation of
PI3K, Akt and NFκB pathways [34,35]. One study,
conducted on cerebral cortical neurons and other cell lines,
showed that VEGF inhibits apoptosis through the activation
inhibitor of apoptosis protein (XIAP) and Bcl-2 [36]. VEGF
has a protective role against oxidative stress and mutant
SOD1-mediated motor neuron death via activation of the
PI3K/Akt pathway [37].
It has been observed that glia may have an important role in
neurodegeneration in ALS. VEGF influences the growth and
differentiation of astrocytes in the CNS; it has gliotrophic
effects via the mitogen-activated protein kinase/
extracellular signal-related kinase and PI3K signaling pathways
[38]. Krum and Khaibullina demonstrated that inhibition of
endogenous VEGF influences the revascularization and
proliferation of astroglia in the brain [39]. This finding
indicates a significant role for VEGF in the repair of CNS
tissue after injury. VEGF also induces the proliferation of
microglial cells in the brain [40]. The main problem with the
above investigations is that they were conducted on
experimental animal models and all of the protective
functions of VEGF have not yet been confirmed in humans.
The activities of VEGF warrant further clinical research
and/or neuropathological studies of human ALS because it
is not certain that VEGF has a protective effect in this
context.
It appears that migration of neural progenitors is an
important process for repairing the CNS. VEGF can
influence stem cells, including neural progenitors, and it is
also known that VEGF mRNA and its receptors are
expressed in neural stem cells [41]. Zhang et al showed that
progenitor cells may express VEGF receptors and that
VEGFR2 mediates the effect of VEGF on progenitor
migration [42]. According to Brusselmans et al, VEGF is a
survival factor for embryonic stem cells during hypoxia [43].
Experiments showed that hypoxia increases the expression
of VEGF and its receptor in neural stem cells, resulting in the
inhibition of apoptosis [44]. Additionally, it has been
demonstrated that the gene transfer of VEGF into neural
stem cells reduces apoptosis caused by hypoxia [45]. This
finding indicates that VEGF has a protective role on neural
Does VEGF represent a potential treatment for amyotrophic lateral sclerosis? Iłżecka 55
stem cells and neurogenesis in the adult nervous system.
The investigation of VEGF function in the developing brain
showed that the inactivation of this growth factor leads to
neural damage of the brain tissue [46].
Judging by these protective effects of VEGF, this growth factor
may have clinical utility in the treatment of different diseases,
including ischemic disorders such as stroke or myocardial
infarction. It may also have an application in the therapy of
different neurodegenerative diseases, including ALS. However,
there are some concerns with the clinical use of this growth
factor and, furthermore, the protective effects of VEGF
described above have not yet been confirmed in humans.
VEGF and ALS
There is evidence to suggest that VEGF may play a
protective role in ALS. It is known that the expression of
VEGF is upregulated by hypoxia, which increases
transcription because of the higher stability of VEGF mRNA,
and through the binding of the transcription factor hypoxiainducible
factor-1 to the 5'-promoter region [47]. In contrast,
it has been demonstrated that the hypoxic induction of
VEGF in SOD1 transgenic mice (an animal model of ALS) is
selectively impaired from a very early stage. The high
baseline and the low hypoxia-induced expression of VEGF
has been observed in the spinal cord of SOD1 mutant mice
[48]. Downregulation of VEGF expression in the spinal cord
of G93A SOD1 rats has also been shown [49]. One study
showed that deletion of the hypoxia-responsive element in
the promoter region of the VEGF gene in transgenic mice
leads to degeneration of motor neurons [50••]. The increase
in reactive oxygen species production observed in ALS can
activate hypoxia-inducible factors, resulting in the increased
transcription of VEGF [51]. As previously described,
glutamate-mediated toxicity may play an important role in
the pathogenesis of ALS. It is possible that the impairment of
VEGF expression in ALS caused by hypoxia can augment
sensitivity of motor neurons for glutamate-mediated
toxicity. It is also known that glial cells influence VEGF
expression, and a high baseline VEGF level observed in
transgenic SOD1 mice might be the result of astrogliosis or
changes in pro-inflammatory cytokines in the ALS spinal
cord [52]. Thus, changes in VEGF may be due to the
pathomorphological status of glia caused by the influence of
harmful factors, including ischemia and inflammation.
Human genetic studies have shown that there is an
association between VEGF and ALS; two at-risk VEGF
genotypes influence risk for ALS. Moreover, the human
haplotypes that are associated with low VEGF levels
increase the risk for ALS [53••]. Huez et al determined two
homozygous recessive haplotypes of VEGF that are defined
by single nucleotide polymorphisms in the promoter and in
the 5'-untranslated region (5'-UTR) of exon 1 as risk haplotypes
of ALS [54]. Moreover, it was revealed that haplotypes
AAG/AAG and AGG/AGG influence the expression of
VEGF by inhibiting VEGF mRNA transcription and
translation, resulting in diminishing VEGF levels that could
lead to motor neuron death. It has also been suggested that
other regulators of the VEGF pathway, such as VEGFR2 and
NRP1 and their effectors, might influence risk for ALS.

56 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
The results of these genetic studies must be confirmed in
future experiments as it is not clear whether primary genetic
factors are responsible for the effects of VEGF expression.
The fact that oxidative stress also primarily influences
expression and levels of VEGF in these cases cannot be
excluded. Data have shown decreased VEGF plasma levels
in ALS patients compared with controls, but no correlation
was found with the clinical parameters of the disease. In
contrast, Nygren et al observed that VEGF levels remained
unchanged in the spinal cord of ALS patients compared
with controls, but that serum VEGF levels were increased in
ALS patients, probably due to hypoxia [55]. It was observed
that CSF VEGF levels were increased in ALS patients with
long duration of disease and in limb-onset ALS [56].
Another study showed low cerebrospinal fluid VEGF levels
during the first year of ALS, which were independent of
VEGF promoter polymorphism [57]. Thus, there are
discrepancies in the data from human studies and it is
difficult to conclude that changes in VEGF levels may lead to
neurodegeneration in ALS. It is possible that such diverse
results are caused by different haplotypes in the ALS
patients studied. Thus, it is difficult to compare the results
from different studies and to draw the correct conclusions.
The pathomorphological studies conducted on the spinal
cord and brain of ALS patients could provide further
information concerning VEGF expression and function in
the CNS.
It was hypothesized that decreased VEGF levels could
influence the neurotrophic and angiogenic activity of this
growth factor. The mechanism of motor neuron loss in ALS
has not been elucidated, but it appears that decreased VEGF
levels could affect blood flow in the spinal cord, which
influences the life span of motor neurons. It is possible that
reduced neural perfusion caused by decreased VEGF levels
may be due to affected vasoregulation, possibly via nitric
oxide activity. Conversely, decreased VEGF levels may also
affect the activity of perivascular autonomic nerves that can
lead to the impairment of vascular tone and spinal cord
perfusion [58•]. Additionally, decreased VEGF levels might
diminish its neurotrophic activity on motor neurons. There
is evidence that impaired VEGF regulation in mice leads to
reduction of spinal cord VEGF levels, especially during
hypoxia, resulting in a neural blood flow reduction of 50%.
Motor neurons are more vulnerable to hypoperfusion, and
chronic ischemia of the spinal cord can cause motor neuron
degeneration. Decreased regional cerebral blood flow has
been observed in ALS patients [59], yet its connection to
VEGF levels has not been investigated. According to
Lambrechts et al, sufficient VEGF levels in humans with high
VEGF-producing genotypes protect the perfusion of
neurons, but the low levels of this cytokine may be a risk
factor for ALS [60•]. It seems that the above mentioned
mechanism might play a role in neurodegeneration in ALS,
but this requires further research.
Muscle atrophy is one of the signs of disease in ALS. It was
revealed that VEGF stimulates the regeneration of skeletal
muscles via the protection of myogenic cells from apoptosis
and the stimulation of growth of myogenic fibers. On
balance, it was observed that progenitor cells from bone
marrow, which are induced by VEGF, can also influence the
regeneration of muscle [61]. Thus, theoretically, VEGF could
inhibit muscle damage in ALS and might be useful for
muscle protection therapy in this disease, but no clinical
studies have yet confirmed this.
The protective effects of VEGF that have been demonstrated
in experimental studies have not been confirmed in clinical
trials. Data have shown that treatment with a variety of
different growth factors, including ciliary neurotrophic
factor, insulin growth factor, glial cell-derived neurotrophic
factor (GDNF) and brain-derived neurotrophic factor, did
not significantly influence ALS. It was suggested that the
inefficiency of treatment using growth factors was caused by
the subcutaneous route of their administration and was the
result of the limited ability of the growth factors to cross the
blood-brain barrier (BBB) [62]. It is possible that the transfer
of VEGF across the BBB using viral vectors might be the best
route of administration, and it is suspected that VEGF
therapy could be most effective in the earliest phase after the
clinical signs of ALS onset. Experiments conducted on a
transgenic mouse model of ALS showed that VEGF may be
an effective treatment after disease onset and can delay
initiation and slow progression of the disease [63••,64••].
Thus, the application of this therapy to humans, especially
in the earliest phase of the disease, requires evaluation in
extensive clinical studies. Storkebaum et al [65] showed that
intracerebroventricular delivery of recombinant VEGF in the
transgenic SOD1 rat model of ALS delays disease onset and
prolongs survival of animals. Based on available data, the
transplantation of genetically modified cells into the CNS
may be a promising strategy for the delivery and expression
of different neurotrophic factors, including VEGF. It has
been suggested that the specific promoters may control the
gene expression that is required for dose-specific and timespecific
therapy [66]. VEGF can be delivered into the CNS by
several routes, including as a recombinant protein, and
through delivery of the gene as a naked plasmid or via viral
vector [67]; these routes of administration are promising for
clinical therapy. Studies are continuing, and it has been
demonstrated that using adeno-associated virus as a vector
for gene delivery into motor neuron-like cells may be an
important strategy in the future treatment of ALS [68]. Klein
et al showed GDNF delivery using human neural progenitor
cells in a rat model of ALS [69]. Another potential treatment
option is via the administration of the heat shock protein coinducers,
which influence cell stress response to cell
protection [70]. However, it is difficult to evaluate the effect
of such therapy in human ALS.
Stem cells
Human embryonic stem cells and neural stem cells can be
used in reparative therapy in ALS. Human neural stem-cellderived
cholinergic neurons can innervate muscle in motor
neuron-deficient adult rats [71], and Vastag observed
partially reversed paralysis in a rat model of ALS after stemcell
therapy [72]. However, there are no data concerning the
influence of stem cells on clinical signs in human ALS,
although stem-cell transplantation had a protective effect in
animal models. The mechanisms of stem-cell protection are
unclear, but it has been suggested that cell fusion,

neurotrophic factor release, including VEGF, endogenous
stem-cell proliferation and transdifferentiation may all play
a role [73].
Stem-cell therapy may be a promising treatment for ALS
[74]. It is known that VEGF promotes the maturation of
neurons and endothelial cells by influencing stem cells that
support reparative processes in the nervous system. The
therapeutic effect exerted by embryonic and neural stem
cells might, at least in part, be mediated by the secretion of
VEGF. The protective effect of non-invasive cell-based
therapy of ALS has been observed by using intravenous
administration of human umbilical cord blood cells in a
mouse model of ALS [75]. It might be interesting to apply
such non-invasive therapy in humans, but there are no data
concerning clinical trials of this nature. The transplantation
of neurons and glia using human motor neuronal progenitor
cells or xenografts of animal cells has also been proposed.
However, in a rat model, Li et al demonstrated that grafted
cells do not migrate and die by apoptosis [76]. One clinical
study showed that the intraspinal cord implantation of
autologous mesenchymal stem cells was safe [77], but this
result needs confirmation in other studies. According to
Silani et al, stem-cell therapy should be used in combination
with other treatments, such as trophic factors, including
VEGF [78]. Moreover, it was demonstrated that combined
cord blood stem cells and gene therapy induced
angiogenesis and improved cardiac performance in a mouse
model of acute myocardial infarction [79]. Thus, this
combined therapy could be promising for the future in ALS,
although there are no data concerning clinical trials of such
therapy. However, in the past, different combined therapies
have been applied in ALS patients and their effect did not
bring any significant clinical improvement.
Protein aggregates
The aggregation of proteins is a typical pathomorphological
hallmark of different neurodegenerative diseases, including
ALS [80]. Some publications indicate that the toxicity of protein
aggregates may be responsible for neurodegeneration. Yang et
al demonstrated that VEGF diminishes β-amyloid-induced
neurotoxicity in Alzheimer's disease through the inhibition
of β-amyloid aggregation and the production of reactive
oxygen species [81]. VEGF may also attenuate toxicity of
protein aggregates in ALS. This needs clinical investigation,
but it appears that using VEGF for the inhibition of
aggregates in ALS might be an interesting therapeutic
strategy. It is also possible that other components of the
VEGF pathway might play a role in motor neuron death.
These include other VEGF receptors and their signaling
effectors [82].
Conclusions
In recent years, attention has been focused on the role of
gene therapy and stem-cell therapy for ALS. Based on
available data, it seems that VEGF could be an important
growth factor for ALS therapy. The protective function that
VEGF exerts via its angiotrophic, neurotrophic and
gliotrophic effects might inhibit neurodegeneration in ALS.
Additionally, the protective effect of VEGF on stem cells of
adult CNS tissue could support reparative processes in ALS
Does VEGF represent a potential treatment for amyotrophic lateral sclerosis? Iłżecka 57
and slow neurodegeneration. It is known that endogenous
precursors or stem cells can differentiate into new
corticospinal motor neurons in the adult brain and
molecular modification of their activity by VEGF might
influence cell death. However, there are some limitations to
using this cytokine clinically, in that the beneficial effect of
VEGF therapy that has been observed in animal models has
not been confirmed in clinical trials. Moreover, there are
some technical difficulties surrounding the delivery of VEGF
into the human CNS. It is known that the application of
different growth factors in clinical trials did not have a
significant effect, but gene therapy to deliver VEGF into
spinal cord and brain, or combined therapy with stem cells,
should be considered as a future treatment for ALS.
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60
Ispronicline Targacept
Hugo Geerts
Address
In Silico Biosciences Inc
3741 Walnut Street #609
Philadelphia
PA 19104
USA
Email: Hugo-Geerts@In-Silico-Biosciences.com
Current Opinion in Investigational Drugs 2006 7(1):60-69
© The Thomson Corporation ISSN 1472-4472
Targacept (formerly a subsidiary of RJ Reynolds) is developing
ispronicline, the lead in a series of nicotinic acetylcholine
(nACh) ligands, as a potential oral treatment for cognitive
impairment, including a variety of non-Alzheimer's dementias.
In July 2005, Targacept was preparing for a phase II study in
patients with mild-to-moderate Alzheimer's disease.
Introduction
With the observation that a nicotinic acetylcholine receptor
(nAChR) deficit occurs in neurodegenerative conditions,
such as Alzheimer's disease (AD), and in psychiatric
conditions, such as schizophrenia, there came a considerable
interest in developing nicotinic receptor modulators with a
less addictive and toxic profile than nicotine [624142],
[624143]. Although different nAChR subtypes exist in the
central nervous system (CNS) as hetero- or homomeric
assemblies of α and β subunits, there is evidence that α7
homomeric and β2-containing (β2*) receptor subunits
predominate in the human brain, as do α3β4 subunits to a
lesser extent [638395], [638396], [638398]. The majority of the
β2* subunits are of the α4β2 nAChR subtype and positron
emission tomography (PET) imaging data in humans have
indicated a high density of this subtype in the cortex and
thalamus [638427]. Although the majority of data suggest
that β2* nAChR subtypes are selectively affected in AD,
other results suggest that α7 nAChR subtypes are also
involved. It is of particular interest to note that in
schizophrenic patients, both genetic and neuropathological
findings suggest that the cognitive deficit is sensitive to
nicotinic receptor modulation. The National Institutes of
Health-sponsored MATRICS (Measurement And Treatment
Research to Improve Cognition in Schizophrenia) project
developed a standardized battery of cognitive tests and
identified a number of pharmacological approaches,
including nAChR modulation [624144], [624147]. The
follow-up project, called TURNS (Treatment Units for
Research on Neurocognition in Schizophrenia), selected
ispronicline (TC-1734; Targacept Inc) for a pilot phase II
study as an add-on medication with a neuroleptic agent
[631107]. Ispronicline is currently undergoing phase II
trials by Targacept for the potential treatment of ageassociated
memory impairment (AAMI) and mild
cognitive impairment (MCI) [545766]. A phase II study in
AD has also commenced [611220]. Targacept is considering
ispronicline for clinical development in indications such as
cognitive impairment (associated with schizophrenia and
following coronary artery bypass grafting), attention
deficit hyperactivity disorder (ADHD) and some forms of
dementia [624033].
Originator Targacept Inc
Status Phase II Clinical
.
Indication Cognitive disorder
.
Actions Neuroprotectant, Nicotinic ACh agonist, Nootropic
agent
Synonyms & Analogs CLZ-52, CLZ-59, nicotinic ACh
ligands (cognitive disorder), nicotinic ACh ligands (memory
enhancers), RJR-1594, RJR-1595, RJR-1734, RJR-2559,
TC-01695, TC-1698, TC-1707, TC-1709, TC-1734, TC-
2248, TC-2258, TC-01706, TC-01707, TC-01714, TC-
01893, TC-02116, TC-02123, TC-02248, TC-02258, TC-
02531
Registry No: 252870-53-4
C
H 3
CH 3
O
N
It has also been proposed that nicotinic receptor stimulation can
provide neuroprotection against some aspects of AD (βamyloid
and glutamate pathology) [622041]. The fact that
galantamine, a cholinergic drug that also has an allosteric
potentiating ligand effect on nAChRs, is used to treat AD
patients, opens a window onto the possible clinical potential of
nicotinic receptor modulation. As a consequence, the
modulation of nicotinic receptors is an interesting therapeutic
approach that is being pursued by a number of laboratories
because, in principle, it combines symptomatic treatment with
neuroprotection [516203], [634638].
Synthesis and SAR
Compounds modulating nAChRs were identified using
Targacept's proprietary Pentad in silico technology [430095],
[512600]. A number of compounds with low nanomolar
affinities for the nAChR were identified, but the in vivo halflives
of these compounds were estimated to be too short. An αmethyl
group was identified as being essential for increasing
the half-life of these compounds from 0.5 to 1.4 h in rodents, as
illustrated by the fact that RJR-2403 (Targacept Inc/Dr Falk
Pharma GmbH), a neuronal nicotinic receptor ligand in
development for the treatment of ulcerative colitis, was rapidly
metabolized through N-demethylation and oxidation. As a
result of a 'use-patent' problem, clinical development of RJR-
2403 was suspended and the in vitro nicotinic receptor α4β2
specificity of ispronicline was investigated. Ispronicline is the 3isopropoxy-pyridine
analog of RJR-2403 synthesized to prevent
N-demethylation. It conferred potent neuroprotection and
dopamine release in rat striatum, without reacting with any
other ganglionic or muscle receptors [345007], [557048].
In order to prepare ispronicline, (S)-N-methyl-N-(tertbutoxycarbonyl)-4-penten-2-amine
and 3-bromo-5-isopropoxy-
CH 3
H
N
CH 3

pyridine were coupled via a palladium-catalyzed Heck
coupling reaction. The resulting intermediate, (S)-(E)-Nmethyl-N-(tert-butoxycarbonyl)-5-[3-(5-isopropoxy-pyridin)yl]-4-penten-2-amine,
was subsequently treated with 6 M
hydrochloric acid in dimethylformamide to give the free
base of ispronicline [559979].
Preclinical development
Ispronicline is a high-affinity (Ki = 11 nM) agonist of nicotinic
receptors in rat brain membrane preparations (nicotine Ki = 4
nM) [306443], [363337] and reportedly has specificity for α4β2
nAChRs [306443]; in one study in rat hippocampal membranes,
ispronicline was ineffective at displacing [ 125I]α-bungarotoxin
binding to α7 nAChRs (Ki > 50,000 nM) [559979]. No further
data on the affinities for other brain nAChR subtypes are
available.
Ispronicline did not bind to muscle-type (α1β1δγ) or
ganglion-type (α3β4) peripheral nAChRs at concentrations
up to 100 µM, as determined by isotopic ion efflux in the
human TE671/RD and rat pheochromocytoma PC12 cell
lines, which express the respective receptors. Conversely,
nicotine activated nAChRs in the human and rat cells with
EC50 values of 60 and 20 µM, respectively, suggesting that
ispronicline has considerable CNS/peripheral nervous
system specificity [306443], [376757]. No other data were
provided regarding human nAChRs.
Induction of dopamine release in rat striatal synaptosomes
showed that ispronicline had a profile comparable to that of
nicotine at these receptors (EC50 = 106 nM and Emax = 85%).
In thalamic synaptosomes, ispronicline increased ion influx
to an Emax of 58% with an EC50 value of 220 nM, compared
with an Emax of 100% and an EC50 value of 590 nM for
nicotine [306443], [376757]. These data are in agreement with
observations that striatal dopamine release is regulated by
β2* nAChRs [636359] and confirm the preference of
ispronicline for the α4β2 nAChR subtype. Given the
preferential localization of α4β2 nAChRs in the thalamus
[638427], the effect of ispronicline on thalamic synaptosomes
is also very likely mediated via these receptor subtypes.
Ispronicline improved performance in a rat radial arm maze
model in vivo, and significant improvements in cognition were
observed following oral administration of ispronicline (0.1, 0.3,
0.6, 3.0 and 6.0 µmol/kg) in both acute (presumed to be singledose)
and chronic (daily for 6 days) schedules [306443]. The
effects on short- and long-term memory in this model
reportedly lasted for 18 to > 24 h [325629], [363337], [363536].
In a murine behavioral despair model, ispronicline showed
significant activity following intraperitoneal administration of 1
and 3 µmol/kg, but not 10 µmol/kg, and was more effective
than the dibenzazepine antidepressant imipramine (40
µmol/kg ip), showing its potential for additional beneficial
effects as an antidepressant [559979].
Ispronicline (0.6, 1.0 and 3.0 µmol/kg) [559979] reversed
scopolamine-induced cognitive deficits in a rat passive
avoidance model (ED50 = 0.89 µmol/kg) with an inverted Ushaped
dose response. This result suggests a possible effect
Ispronicline Geerts 61
on pre-synaptic ACh release and the subsequent stimulation
of post-synaptic muscarinic receptors, because scopolamine
is not documented to have any effect on nicotinic receptors.
This finding is corroborated by the observation that a
synergistic effect was achieved in this model when a suboptimal
dose of ispronicline (0.6 µmol/kg) was combined
with ineffective doses of the acetyl cholinesterase (AChE)
inhibitors tacrine and donepezil. Ispronicline combined with
each inhibitor resulted in an enhanced step-through latency
compared with sole ispronicline administration. Stepthough
latencies (as % of control) were as follows:
unlesioned, 69%; scopolamine lesioned, 8%; ispronicline (1.0
µmol/kg), 55%; tacrine (12 µmol/kg), 36%; donepezil (1.0
µmol/kg), 53%; suboptimal ispronicline (0.6 µmol/kg),
tacrine (1.2 µmol/kg) or donepezil (0.1 µmol/kg), 21, 6 and
21%, respectively; and suboptimal ispronicline plus tacrine
or donepezil: 37 and 39%, respectively [345774], [559979].
Ispronicline (7 to 14 days at an unstated dose) reduced
spontaneous locomotor activity in rats in a monophasic
manner, unlike the biphasic activity of nicotine, for the
duration of the test (90 min). Chronic administration of the
compound resulted in rapid tolerance [345791]. This
property might necessitate innovative dosage scheduling in
the clinic.
Acute oral administration of ispronicline dose-dependently
increased levels of free ACh in the cortex of rats [475601],
[557048]. The lowest active dose was 5 mg/kg and the
maximally effective dose was 10 mg/kg, and these yielded
increases of 36 and 70% over the basal ACh values,
respectively. The maximal effect was observed at the 10mg/kg
dose. A larger dose of ispronicline (20 mg/kg)
increased the duration of ACh release (to 4 h), but did not
increase the amplitude significantly (84%). With different
doses of nicotine (1.0, 2.5 and 5.0 mg/kg po), the amplitude
of the stimulated ACh response did not change, and the
maximal increases over the basal levels of ACh were 47, 44
and 56%, respectively, 40 to 80 min after treatment. The nonselective
nAChR antagonist mecamylamine (Targacept Inc),
which is in development for the potential treatment of
various neuropsychiatric disorders, inhibited the ACh
release induced by ispronicline and nicotine (maximal
effective doses) at a dose of 1 mg/kg when administered
subcutaneously 40 min before dosing with ispronicline and
nicotine. Oral administration of ispronicline improved object
recognition in mice after 24 h. The recognition index (RI) in
mice treated with the vehicle was 72 ± 5 after 3 h and 45 ± 2
after 24 h; however, after treatment with 0.5 and 1 mg/kg
ispronicline, the RI at 24 h improved to 72 ± 3 and 55 ± 3,
respectively. Both these effects, the increases in ACh
concentration and improved object recognition, were also
countered by mecamylamine [475601]. After a repeated
treatment of 4 days with ispronicline (10 mg/kg) or nicotine
(1 mg/kg), no tolerance was observed regarding ACh
release [376757].
Ispronicline was neuroprotective in an N-methyl-D-aspartate
(NMDA)-induced cell-death paradigm and may be
synergistic with current AD therapies [325629]. In a
hippocampal slice model (a mature culture of fetal rat
neurons) subjected to a 15-min hypoxia/glucose deprivation

62 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
episode, ispronicline prevented the loss of synaptic
transmission in a concentration-dependent manner, with a
maximal effect of > 70% protection at 10 µM. The effect was
mediated through nAChRs because mecamylamine, blocked
the neuroprotective effect [583306]. This effect is somewhat
unexpected given the proposed link between specific α7
nAChR activation and neuroprotection. Neurotoxicity
stimulated by glutamate is prevented by nicotine in primary
cultures of cerebellar neurons and is generally thought to be
mediated by α7 nAChR activation. However in acutely
dissociated slices, neuroprotection by nicotine can be mediated
by activation of α4β2 nAChRs and inhibition of α7 nAChRs
[638430]. Therefore, neuroprotection by ispronicline can be
explained by its preferential activation of the α4β2 nAChR.
The mechanism of ispronicline neuroprotection reportedly
utilizes a signal transduction pathway involving JAK2, PI3
kinase, Akt and Bcl-2 [467878]. Ispronicline (unstated dosage)
was orally active in vivo and induced sustained ACh release
from the cortex, showing potency in animal models of cognition
and attention, and additivity/synergy with AChE inhibitors. It
demonstrated neuroprotective effects in chemically induced
neuronal excitotoxicity models and in hypoxia/glucose
deprivation models. Additionally, ispronicline showed
antidepressant activity; however, no details were provided for
these studies [513286].
Metabolism and pharmacokinetics
Metabolism studies conducted in vitro with liver microsome
preparations from mice, rats, guinea pigs, dogs, monkeys
and humans identified five metabolites; the O-dealkyl
derivative endogenous conjugate was the primary
metabolite in humans and monkeys, while the N-oxide
metabolite was present in all other species [559979]. The
affinities of the 3-alkylcarbonate and N-desalkylated
metabolites for α4β2 nAChRs were approximately 20- and
40-fold higher than for ispronicline; other metabolites had
affinities > 100-fold over ispronicline. In Sprague Dawley
rats that were administered 20 mg/kg of ispronicline, mass
spectroscopy identified 12 metabolites in the plasma, the Odealkyl
derivative being the major metabolite. No
metabolites were detected in fecal extracts, although a small
amount of the parent compound was present [559979].
Ispronicline had a half-life of 1 to 2 h in rodents [557048],
[634416]; however, given that the beneficial effect of a single
oral administration of ispronicline on cognition in preclinical
models persisted for 18 to 48 h [363337], [634416], this halflife
does not seem to present much of a problem for efficacy.
This unexpected long-term potentiation effect might be
because of a much higher retention of the compound in the
brain, an elaborate downstream effect leading to transient
intracellular plasticity changes, or both. In Sprague Dawley
rats, oral administration of ispronicline (10 mg/kg)
produced high systemic levels, with a maximal plasma
concentration (Cpmax) of 370 ng/ml and Tmax value of 0.25 h.
The compound was cleared rapidly, with a termination halflife
of 1.1 h. The bioavailability of ispronicline was 73.3%.
Whole-brain ispronicline levels at this dose were high
(maximal brain concentration (Cbmax) = 659 ng/g; Tmax = 0.5
to 2 h), showing that the drug readily penetrated the brain.
After intravenous administration of 1 mg/kg, ispronicline had
a half-life of 0.8 h and was cleared rapidly (7.1 l/h/kg
compared with the hepatic plasma flow of 2 to 4 l/h/kg)
[559979].
In dogs, ispronicline had a half-life of 2 h following a 1mg/kg
intravenous dose. A high total plasma clearance of
3.2 l/h/kg was achieved compared with the hepatic plasma
flow of 1.2 to 2.4 l/h/kg. Following oral administration of 1
mg/kg ispronicline, low systemic plasma levels were
achieved (Cpmax = 35 ng/ml at 0.5 to 2 h). The elimination
half-life of ispronicline was 1.3 h and its estimated
bioavailability was 31.4% [559979].
In a crossover study in six healthy male volunteers,
ispronicline (2 to 320 mg po) had a Tmax at 2 h and an
elimination half-life of 4 h; following a 320-mg dose,
ispronicline had a Cmax of 120 ng/ml, a plasma concentration
5- to 10-fold greater than that expected to produce maximal
cognitive effects [559979].
In elderly AAMI patients (> 60 years of age), a 50-mg oral dose
of ispronicline gave rise to a plasma Cmax range of 4 to 25 ng/ml
[612281], and oral doses of 25 to 75 mg ispronicline produced
plasma Cmax values in the range of 4 to 55 ng/ml [634952].
These low Cmax values might be due to extensive metabolism,
high plasma clearance or low bioavailability. A complete
pharmacokinetic study of a single 80-mg dose of ispronicline
was performed in six elderly volunteers to assess its absorption,
distribution, metabolism and excretion properties. Cognitive
improvement was evident after 36 to 48 h, which was
comparable to the long duration of action observed in animal
models, thus indicating the suitability of a once-daily dosing
schedule [615362]. The study showed that ispronicline had a
half-life of 5 to 7 h in humans [634416]. Another study in six
fed/fasted volunteers examined food interaction following an
80-mg dose of ispronicline, although the results from this study
have apparently not yet been reported [615362].
Toxicity
The results of studies in rats, dogs and rabbits indicated that
ispronicline was free from toxic effects at the doses tested. In
rats, no effect was observed on diaphragm contraction,
respiratory function or gastric emptying after oral
administration of up to 50, 250 and 500 mg/kg, respectively.
In rats and dogs that were chronically administered
ispronicline for 13 weeks (50 and 30 mg/kg, respectively),
the only side effect was slight and transient bradycardia in
dogs at the highest dose, possibly mediated by autonomic
nerve stimulation [512176]. Overall, ispronicline was well
tolerated in animals and there was no indication of
reproductive, cellular or genetic toxicity [513286].
Other preliminary toxicology studies showed a low toxicity
for ispronicline, with observable adverse effects occurring in
normal male and female rats at doses of 5 to 200 mg/kg,
compared with cognitive enhancement at 0.034 mg/kg. At a
dose of 1400 mg/kg, significant toxicity was produced
without causing death in rats [325629]. Thus, the therapeutic
effects of ispronicline in animals are dissociated from its side
effects by four to five orders of magnitude [467878].

In a study conducted in rats trained to discriminate nicotine,
ispronicline and the known addictive properties of nicotine
were compared. Nicotine engaged appropriate responding in
70% of animals at a dose of 1.9 µmol/kg compared with
ispronicline, which engaged an equivalent response only at a
dose of 40 µmol/kg; this result indicates an approximately 20fold-reduced
propensity for dependence of ispronicline
compared with nicotine [559979].
Clinical development
Phase I
Four phase I trials of ispronicline, which assessed safety,
pharmacokinetics and cognitive enhancement, have been
completed. One study tested eight escalating single oral doses
of ispronicline (2, 4, 10, 20, 40, 80, 160 and 320 mg) in 48 healthy
volunteers [559979], and a multiple escalating-dose trial (50, 100
and 200 mg) was conducted in 24 healthy volunteers over a 10day
period [511071], [615362]. A pharmacokinetic study that
tested food interaction in six elderly volunteers was also
completed. The rapid absorption, dose proportionality and
favorable plasma half-life of ispronicline in these trials
suggested the suitability of a once-daily dosing schedule. No
safety issues were reportedly encountered and dose-specific
enhancement of both direct and surrogate measures of memory
and attention was observed. No differences in the quality of
working memory factor were observed. Less pronounced
improvements were observed in the 100-mg group, compared
with all other doses, indicative of a possible inverted U-shaped
dose-response curve [615362].
In the single and multiple escalating-dose trials, ispronicline
dose-dependently induced electrical brain activity characteristic
of a nicotine agonist, and electroencephalogram (EEG) analysis
confirmed its CNS penetration and activity. In addition, dosespecific
effects were observed on direct and surrogate measures
of memory in a computerized cognitive test battery [615362]. In
line with preclinical observations, the compound induced longlasting
cognitive enhancement for up to 48 h in elderly
volunteers [592125]. In the single and multiple escalating-dose
trials, EEG analysis showed that orally administered
ispronicline caused a shift in relative and absolute power from
lower to higher frequency bands. Specifically, power shifted
from the α1 to the α2 band. The shift in dominant α suggested
that the compound had entered the brain and was typical of a
nicotine agonist. Similar effects were observed in both trials on
day 1 and in the multiple escalating-dose trial on day 10. No
tolerance to ispronicline occurred over the 10-day dosing period
[634416]. In the multiple escalating-dose trial in healthy
volunteers, 10 days of dosing with ispronicline produced
efficacy in the 'power of attention' measure of the cognitive
drug research (CDR) test battery [634952]. The 100-mg dose of
ispronicline improved memory (notably immediate and
delayed word recall) in volunteers, and a 200-mg dose
improved picture and word recognition and enhanced
vigilance [634416].
In elderly volunteers, pharmaco-EEG changes resembled
those seen in younger individuals; the changes were of an
acceleration type, with power shifting from low to high
frequency bands. In CDR cognitive tests, significant
Ispronicline Geerts 63
differences between ispronicline and placebo on measures of
immediate and delayed recall, picture recognition and
quality of episodic memory were achieved. There was good
correlation between plasma levels of the drug and
pharmaco-EEG changes [634416]. Correlations of
pharmacodynamic and pharmacokinetic data indicated that
plasma Cmax values in the range 4 to 55 ng/ml were
associated with greatest cognitive improvement; Cmax values
in this range would be achieved with oral doses of 25 to 75
mg, levels at which ispronicline has tolerability equivalent to
placebo [634952].
Phase II
In a randomized, double-blind, placebo-controlled, phase
IIa/II study in an undisclosed number of AAMI patients
(aged > 60 years), a single dose of 80 mg ispronicline was
superior to placebo in improving quality of episodic
secondary memory factor score up to 48 h after dosing. After 3
weeks of treatment at 50 mg, significant improvements were
observed in CDR measures of the power and continuity of
attention, episodic memory and speed of thinking, compared
with patients receiving placebo [612281], [634952].
Targacept reports that a phase II trial with ispronicline has
been completed in elderly individuals with AAMI (n = 76).
Positive effects on various aspects of cognition were
observed and the drug was well tolerated at doses up to 150
mg [624033].
Data were presented recently for the double-blind, placebocontrolled,
crossover phase II study of ispronicline in
volunteers with MCI [641513]. Volunteers (aged > 60 years)
with MCI (mini-mental state examination (MMSE) score ≥ 24
and Wechsler memory scale-R, paired associate learning test
score ≥ 1.5 standard deviations lower than age matched
controls) were randomized into cohorts of 20 to sequentially
receive 3 weeks oral treatment with 50 and 100 mg of
ispronicline or placebo, with a 2-week washout between
treatments. Cognitive assessment was performed at 0, 2 and 4 h
post-dosing on the CDR test battery. No effect was observed
with 50 mg of ispronicline (n = 19), at which placebo was
superior to drug on measures of working memory and memory
speed. The 100-mg dose of ispronicline (n = 17) was superior to
placebo in the power of attention and episodic memory factors
(p < 0.05), and on the working memory and speed of memory
tests (p < 0.1). Analysis of data from both dose groups showed
that ispronicline produced greater cognitive improvement in
more severely impaired (MMSE 23 to 27) volunteers than those
with lesser impairment (MMSE = 28 to 30). Ispronicline was
well tolerated and demonstrated a favorable safety profile at
both doses [641513].
A randomized, double-blind, placebo-controlled phase II
clinical trial of ispronicline is ongoing in elderly individuals
(aged 50 to 80 years) with AAMI. Recruitment has been
completed (174 participants were expected), and the study is
scheduled for completion in February 2006
[www.clinicaltrials.gov]. A further phase II trial is planned for
mid 2006, and is designed to evaluate ispronicline as a
monotherapy treatment for mild AD or add-on therapy to
approved medications for moderate AD. Clinical development

64 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
is also being considered for cognitive impairment associated
with schizophrenia and following coronary artery bypass
grafting, ADHD and certain forms of dementia [624033]. In
summary, ispronicline was well tolerated and demonstrated
cognitive enhancing effects in the phase I and phase II clinical
trials to date (n = 200) [611220].
Side effects and contraindications
In phase I/II studies assessing the effect of ispronicline on
central activity and cognitive enhancement, adverse events
were only detected at the maximum tolerated dose of
ispronicline (150 mg in the elderly and 320 mg in the young).
These included headache, dizziness and light-headedness
and occasional nausea/vomiting. These side effects were
attributed to the central pharmacology of ispronicline
because they were not accompanied by changes in
cardiovascular variables as would be expected if peripheral
nAChR inhibition were occurring [615362].
In phase IIa/b trials, ispronicline had an effective dose of 50 to
100 mg, and no toxic effects were observed at 320 mg,
suggesting a broad therapeutic window [541084]. Ispronicline
was well tolerated and demonstrated a favorable safety profile
[612281].
In a phase II study of 50 or 100 mg ispronicline in volunteers
with MCI, the drug was well tolerated at both doses. The
most common adverse event was light-headedness. No
significant effects were recorded on biochemical,
hematological or urinary measures, vital signs or cardiac
monitoring [641513].
Patent summary
In January 2002, Targacept and Aventis Pharma SA
published WO-00205798, a PCT application that covered
salts of ispronicline and their use in the prevention or
treatment of CNS disorders.
Four US patents (US-06432975, US-06624173, US-06440970
and US-06525065) relate to composition of matter of the
chemical family of the hetero-aryl azabicyclo alkanes. In the
composition patents, a broad application domain has been
stated, including the treatment of other CNS conditions and
disorders, such as schizophrenia, in providing neuroprotection,
the management of stroke, and in treating patients
susceptible to convulsions, depression, autism and certain
neuroendocrine disorders.
WO-2005037832 was published by Targacept in April 2005,
and claims the use of ispronicline for the treatment of
Parkinson's disease, Tourette's syndrome, ADHD,
schizophrenia, drug/nicotine addiction, pain and obesity. In
addition, appropriately radiolabeled compounds are
claimed for use as selective probes for nAChR subtypes in
neuroimaging applications in US-06432975.
Current opinion
Specific stimulation of α4β2 versus α7 nAChRs will likely
lead to different effects on cognitive scales because of the
differential distribution of nAChR subtypes (preferentially
striatal-thalamic versus cortical), and differential sensitivity
to pathological conditions (eg, AD versus psychiatric
diseases). In this regard, perhaps something can be learned
from the clinical expertise gained from the study of ABT-418
(an nAChR agonist that was discontinued from
development by Abbott Laboratories in 2002 because of
safety concerns) in a number of medical conditions
involving lack of attention and cognitive deficits. The
compounds have a similar profile in terms of their nAChR
selectivity. Interestingly, unlike ABT-418, ispronicline
produces a sustained cognitive effect in both preclinical and
human models long after its clearance from the body. This
prolonged action might be the result of changes in
intracellular signaling, the nature of which is still unclear. At
the maximal clinical tolerable dose, ispronicline will most
probably also stimulate the α7 nAChR. For α7 nAChRmediated
neuroprotection against β-amyloid, it has been
shown that Janus kinase/Akt pathways are involved in
intracellular activation [621830]. As a possible caveat,
preclinical data suggest that as well as possibly reducing βamyloid
pathology [622041], long-term activation of
nicotinic receptors in transgenic animals can exacerbate tau
pathology [621828]. Whether this is the case for ispronicline
is currently unknown.
The specific activation of neuronal nAChRs is advantageous
because gastrointestinal side effects, such as vomiting and
diarrhea, currently occur in many AD patients during the
titration phase of their treatment with AChE inhibitors, and
are assumed to be related to peripheral muscarinic receptor
activation. Nausea is a more typical nicotinic-receptormediated
side effect, and whether the effects are a
consequence of central activity is still a matter for debate. In
any case, no data have described the incidence of nausea in
ispronicline-treated patients.
The clinical experience with galantamine in AD patients
suggests a superior effect of nAChR modulators in
enhancing attention [516203] and working memory [622036]
over and above that attributable to AChE inhibition alone. In
addition, specific behavioral improvements can be expected
in agitation/aggression, anxiety, disinhibition and aberrant
motor behaviors [622040]. This finding is in line with the
observed effects of ispronicline on CDR battery scales in
cognitively impaired elderly individuals. This clinical effect
is probably because the stimulation of nicotinic receptors,
which diffusely project out of the nucleus basalis of Meynert
and the pedunculopontine nucleus, modulates their
activation in a large part of the brain. This is likely mediated
by an increase in dopamine, serotonin, norepinephrine,
acetylcholine and even glutamate and γ-aminobutyric acid
(GABA) levels. As a specific example, β2* nAChR
stimulation increases dopamine release in the striatum
[636359]. One could argue that increased dopamine release
in a slightly deficient striatum could enhance the saliency of
stimuli and positively influence reward stimuli. However,
the specific nAChR subtype responsible for the other effects
has not been identified in all cases, and specific questions
remain regarding the kinetics of activation, desensitization
and reactivation of the nAChRs responsible, resulting, for
example, in spatial and temporal differences in excitatory

glutamatergic and inhibitory GABA modulation in complex
interacting networks [621790], [621822].
Whether this effect will be sufficient for pure nAChR
agonists to improve cognitive scales such as the Alzheimer's
disease assessment scale cognitive subscale (ADAS-Cog) or
MMSE is at present unknown. Computer simulation of a
virtual synaptic cleft suggests that suboptimal AChE
inhibition can be synergistically amplified by nicotinic
receptor stimulation [621742]. This effect was illustrated in a
number of in vivo preclinical studies in which a dose of
galantamine had similar or superior effects on behavior or
neurophysiology compared with an identical dose of
donepezil, a pure AChE inhibitor [621831], [621833], despite
the fact that donepezil produces a 3- to 4-fold higher brain
AChE inhibition under these conditions [621785]. This
finding suggests that the activation of nAChR through the
combination of nAChR modulation with a low brain AChE
inhibition can actually lead to the same (or even superior)
behavioral or neurochemical changes as direct stimulation in
the context of a much higher brain AChE inhibition.
There is a high probability that ispronicline will be tested in
combination with an AChE inhibitor during clinical
development. Interestingly, combination with a suboptimal
dose of an AChE inhibitor could lead to superior clinical
efficacy on primary endpoints, such as ADAS-Cog, while
simultaneously limiting the development of tolerance owing to
the upregulation of the AChE enzyme as a consequence of
high-level continuous AChE inhibition [622031]. Furthermore,
muscarinic receptor stimulation resulting from limited AChE
inhibition can provide additional benefits for a number of
behavioral problems, as suggested by the clinical experience
with muscarinic M1 agonists (for a review, see reference
[624153]). In addition, muscarinic M1 receptor stimulation can
provide neuroprotection against both amyloid and tau
pathology beyond nicotine receptor activation (reviewed in
reference [621786]). Because the intracellular pathways of both
approaches differ, there may be the possibility of an additive or
synergistic action.
Ispronicline Geerts 65
Ispronicline is also currently in development for the
treatment of pre-Alzheimer's conditions such as MCI and
AAMI. A reactive upregulation of ACh-synthesizing
enzymes has been documented in this patient population,
probably as a consequence of dysfunctional cholinergic
nerve terminals [622042]. This upregulation might reduce
the beneficial effect of direct nAChR stimulation by
modulators such as ispronicline. In this regard, it is
interesting to note that in terms of delaying the diagnosis
of AD, the clinical benefits of AChE inhibition in MCI
patients are, at best, limited [622044]. MCI and AAMI
have not yet been recognized by the Food and Drug
Administration as medical conditions, but the regulatory
landscape might change substantially over the next few
years.
An interesting development is the clinical proof-of-principle
study of ispronicline as an add-on in the treatment of
cognitive deficits in schizophrenia. This study was carried
out by the TURNS project, as presented at the 2005
International Conference on Schizophrenia Research
[631107]. Although the neuropathology and genetics of
schizophrenia suggest a specific α7 nAChR deficit in this
case, a well-balanced modulation of both major brain
nAChR subtypes, such as that provided by ispronicline,
might be of great value.
In summary, the pharmacological profile of available data
for ispronicline indicate that this compound may provide
an interesting new mechanism for treating cognitive
deficits in both schizophrenia and AD. Extrapolating from
the preclinical data for galantamine, a compound with a
similar pharmacology (reviewed in reference [634638]), in
theory we can expect that ispronicline will combine
symptomatic cognitive improvement with general
neuroprotection against β-amyloid pathology. We believe
that the best effects of the drug will be observed in
patients with AD and when it is combined with a
suboptimal dose of an AChE inhibitor.
Development history
Developer Country Status Indication Date Reference
Targacept Inc UK Phase II Cognitive disorder 11-NOV-03 512600
Targacept Inc US Phase II Cognitive disorder 06-JUL-05 611220
Literature classifications
Chemistry
Study type Result Reference
SAR. A number of compounds with low nanomolar affinity for nAChRs were identified, but were metabolized
through N-demethylation and oxidation, resulting in a half-life of 30 min. The 3-isopropoxy-pyridine analog
of RJR-2403 had an improved half-life of 1.4 h in rodents, and was later named ispronicline. An α-methyl
group was identified as being essential for increasing the half-life.
557048
Synthesis. Ispronicline was prepared by coupling (S)-N-methyl-N-(tert-butoxycarbonyl)-4-penten-2-amine and 3bromo-5-isopropoxy-pyridine
via a palladium-catalyzed Heck coupling reaction. The resulting intermediate,
(S)-(E)-N-methyl-N-(tert-butoxycarbonyl)-5-[3-(5-isopropoxy-pyridin)yl]-4-penten-2-amine, was
subsequently treated with 6 M hydrochloric acid in dimethylformamide to give the free base of ispronicline.
559979

66 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Biology
Study type Effect studied Model Result Reference
In vitro Activity. Rat brain membrane preparations, Ispronicline was a high-affinity agonist of
306443
or muscle- or ganglion-type nicotinic receptors in rat brain membranes (Ki =
nAChRs.
11 nM; nicotine Ki = 4 nM), and reportedly had
specificity for nAChRs. Ispronicline did not bind
to the muscle-type (α1β1δγ) or ganglion-type
(α3β4) peripheral nAChRs at concentrations up
to 100 µM. Conversely, nicotine activated
nAChRs in human and rat cells, with EC50
values of 60 and 20 µM, respectively, indicating
greater CNS/peripheral nervous system
specificity for ispronicline.
In vitro Efficacy. Rat striatal and thalamic
In striatal synaptosomes, ispronicline had a 306443
synaptosomes treated with
dopamine-release profile comparable to that of
ispronicline or nicotine (unstated nicotine (EC50 = 106 nM and Emax = 85%). In
concentrations).
thalamic synaptosomes, ispronicline increased
ion influx to an Emax of 58% with an EC50 value of
220 nM, compared with an Emax of 100% and an
EC50 value of 590 nM for nicotine. Given the
preferential localization of α4β2 nAChRs in the
thalamus, this effect is likely mediated by this
receptor subtype.
In vivo Efficacy. Radial arm maze model. Rats were Both schedules of ispronicline significantly
306443
orally administered ispronicline improved both working and reference memory
(0.1, 0.3, 0.6, 3.0 and 6.0 µmol/kg)
in both acute (presumed to be
single-dose) and chronic (daily for 6
days) schedules.
performance.
In vivo Efficacy. Scopolamine-induced deficits in the Ispronicline improved performance both alone 345774
passive avoidance task in rats. (ED50 = 0.89 µmol/kg) and at a suboptimal dose
(0.6 µmol/kg) in combination with tacrine and
donepezil.
Ex vivo Activity. Synaptic transmission after Ispronicline prevented the loss of synaptic
583306
oxygen/glucose deprivation in a rat transmission in a concentration-dependent
brain hippocampal slice model manner, with a maximal effect of > 70%
incubated with ispronicline. protection at 10 µM. The effect was mediated by
nAChRs because mecamylamine, a nonselective
antagonist, blocked the neuroprotective
effect.
Metabolism
Study type Effect studied Model Result Reference
In vivo Pharmacokinetics. Sprague Dawley rats administered Values for Cpmax and Tmax were 370 ng/ml and 559979
a single oral dose of ispronicline 0.25 h, respectively. The compound was
(10 mg/kg).
cleared rapidly, with a termination half-life of
1.1 h. The bioavailability was 73.3%. Wholebrain
ispronicline levels were high (Cbmax =
659 ng/g; Tmax = 0.5 to 2 h), indicating ready
brain penetration. After intravenous
administration of 1 mg/kg, ispronicline had a
half-life of 0.8 h and was cleared rapidly (7.1
l/h/kg compared with the hepatic plasma flow
of 2 to 4 l/h/kg).
In vivo Pharmacokinetics. Dogs administered a 1-mg/kg A high total plasma clearance of 3.2 l/h/kg 559979
intravenous or oral dose of
was achieved compared with the hepatic
ispronicline.
plasma flow of 1.2 to 2.4 l/h/kg. Following oral
administration of 1 mg/kg, low systemic
plasma levels were achieved (Cpmax = 35
ng/ml at 0.5 to 2 h). The elimination half-life of
ispronicline was 1.3 h and its estimated
bioavailability was 31.4%.
In vivo Pharmacokinetics. Elderly AAMI patients (aged > 60 Plasma Cmax values ranged from 4 to 25
612281
years) administered 50 mg of oral
ispronicline.
ng/ml.
In vivo Pharmacokinetics. Elderly volunteers (aged > 60 Plasma Cmax values ranged from 4 to 55
634952
years) orally administered
ng/ml. Ispronicline induced long-lasting
ispronicline (25 to 75 mg).
cognitive enhancement for up to 48 h.

Metabolism (continued)
Ispronicline Geerts 67
Study type Effect studied Model Result Reference
In vivo Pharmacokinetics. A food-interaction trial in six No food interaction was observed. Single 615362
fed/fasted elderly volunteers doses of ispronicline achieved CNS
administered an 80-mg oral dose of penetration. The rapid absorption, dose
ispronicline.
proportionality and favorable plasma half-life
of ispronicline in this trial suggested the
suitability of a once-daily dosing schedule.
Clinical
Effect studied Model Result Reference
Safety and efficacy. A phase I, 10-day multiple
Ispronicline was well tolerated and no safety issues were 615362
escalating-dose study of
encountered up to 200 mg. Dose-specific enhancement of
ispronicline (50, 100 and 200 mg) in both direct and surrogate measures of memory and
young volunteers (n = 24).
attention was observed. No differences were observed on
the quality of working memory factor. Less pronounced
improvements were seen in the 100-mg group, indicative
of an inverted U-shaped dose-response curve.
Efficacy and tolerability. A phase I, single and multiple Ispronicline dose-dependently induced electrical brain 634416
escalating-dose trial of ispronicline activity on EEG, characteristic of a nicotine agonist,
in young volunteers (n = 48 and 24, causing a shift in relative and absolute power from
respectively).
lower to higher frequency bands. No tolerance to
ispronicline occurred over the 10-day dosing period.
Efficacy and tolerability. A phase I trial of ispronicline in Pharmacodynamic and pharmacokinetic data
634952
elderly patients with AAMI (aged > suggested that Cmax values in the range of 4 to 55 ng/ml
60 years).
caused the greatest cognitive improvement. Oral doses
of 25 to 75 mg of ispronicline gave rise to values in this
range, at which ispronicline was tolerated in a similar
manner to placebo.
Efficacy. A phase II, randomized, double- A single dose of 80 mg ispronicline was superior to 612281
blind, placebo-controlled trial in placebo in improving quality of episodic secondary
elderly AAMI patients (aged > 60 memory factor score up to 48 h after dosing. Three
years).
weeks of treatment with 50 mg ispronicline improved
CDR measures of the power and continuity of attention,
episodic memory and speed of thinking, compared with
patients receiving placebo.
Efficacy and tolerability. Phase II trials in elderly AAMI Positive effects on various aspects of cognition were 624033
patients (n = 76).
observed, and the drug was well tolerated at doses up
to 150 mg.
Associated patent
Title Pharmaceutical compositions and methods for use.
Assignee Targacept Inc; Aventis Pharma SA
Publication WO-00205798 24-JAN-02
Priority US-20000616743 14-JUL-00
Inventors Dull GM, Leconte J-P, Kabir H.
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2005 September 21 Abs 105

70
AEOL-10150 Aeolus
Richard W Orrell
Address
Department of Clinical Neurosciences
Royal Free and University College Medical School
University College London
Rowland Hill Street
London
NW3 2PF
UK
Email: r.orrell@medsch.ucl.ac.uk
Current Opinion in Investigational Drugs 2006 7(1):70-80
© The Thomson Corporation ISSN 1472-4472
AEOL-10150, a small-molecule antioxidant analogous to the
catalytic site of superoxide dismutase, is under development by
Aeolus (formerly Incara) as a potential subcutaneous treatment
for amyotrophic lateral sclerosis (ALS), stroke, spinal cord
injury, lung inflammation and mucositis. The compound is
currently undergoing a phase I clinical trial for ALS. In
October 2005, the company had applied for Fast Track status,
and planned to submit a special protocol assessment for a
pivotal phase II/III trial.
Introduction
AEOL-10150 is a manganese metalloporphyrin catalytic
oxidant, a small-molecule antioxidant that has structural and
functional similarities to the catalytic site of superoxide
dismutase (SOD). Metalloporphyrins are a novel class of
antioxidants that 'scavenge' a wide range of oxidative species,
including superoxide, peroxide, peroxynitrite and lipid peroxyl
radicals [449960], [625113]. AEOL-10150 is under development
by Aeolus Pharmaceuticals Inc (formerly Incara
Pharmaceuticals) as a potential subcutaneous treatment,
primarily for amyotrophic lateral sclerosis (ALS) [505222], but is
also under investigation for a range of conditions, including
stroke [428437], spinal cord injury [616364], lung inflammation
[616377] and mucositis [432294].
ALS is a neurodegenerative disorder affecting men and
women of all ages and ethnic origins worldwide. ALS may
also be called motor neuron disease. This disorder has an
annual incidence rate of approximately two per 100,000 of
the population, and a prevalence of six per 100,000. The
incidence increases with age, with the mean age of onset
being approximately 60 years, although it can affect
individuals from early adulthood (from approximately 20
years) onwards. Men are slightly more likely to be affected
than women (1.4:1) [478835], [638196], [638197]. The
progression of the disease is typically rapid, with the earliest
symptom often being a muscle weakness in the arms or legs
of a patient, coinciding with an increased tendency to drop
objects, stumble, twitch or experience abnormal fatigue in
the limbs. Further weakening and paralysis can spread to
the muscles involved in breathing, swallowing and speech,
leading to immobility, an inability to eat, drink and speak,
and respiratory failure. Early respiratory or bulbar
symptoms are adverse prognostic indicators of the disease.
Respiratory failure is the most common cause of death in
ALS, and usually occurs within three to five years of onset
[478835], [638197], [638203]. Following the onset of
symptoms, over 50% of ALS sufferers will die within three
Originator Aeolus Pharmaceuticals Inc
Status Phase I Clinical
.
Indications Cerebrovascular ischemia, Lung inflammation,
Motor neuron disease (amytrophic lateral sclerosis),
Mucositis,.Spinal cord injury.
.
Actions Antioxidant agent, Neuroprotectant
.
Technology Subcutaneous formulation
Registry No: 286475-30-7
C
H 3
C
H 3
N +
N +
N
N
CH 3
N
N
N
N
N N
CH 3
Mn 3+
CH 3
CH 3
N +
N +
Cl Cl Cl Cl Cl
years, with < 10% living beyond five years. Disease
progression can be either more rapid or greatly reduced in
some cases, with around 10% of patients living for > 10 years
[634304].
The cause of ALS remains unknown, although free-radicalmediated
neurotoxicity is one proposed mechanism
[638229], [638230]. Free-radical-mediated toxicity has been
implicated in a wide range of diseases, including
neurodegenerative diseases, stroke, acute myocardial
infarction, inflammatory disorders and carcinogenesis
[449960], [638218]. In addition, a proportion of patients with
ALS (approximately 2%) have mutations of the gene
encoding the copper/zinc SOD1 enzyme [400330], [638203],
[638220], [638223]. Current evidence suggests that in patients
with SOD1 mutations, the disease is not related to deficiency
of SOD activity, but is caused by a toxic gain of function,
possibly related to protein accumulation or other
mechanisms [638223], [638233].
Current treatment for ALS is largely supportive, and only
one medication has been licensed. Riluzole is orally
administered, and is proposed to inhibit glutamate release.
Although well tolerated, the drug has limited efficacy.
Glutamate-induced neuronal excitotoxicity is one
hypothesized cause of ALS, hence the initial study of
riluzole. The therapeutic mechanism of action remains
uncertain, however, and other possibilities include an effect
on modulation of sodium, potassium or AMPA/kainate
channels [262608]. Evidence from clinical trials indicates a
CH 3
CH 3

prolongation of survival of approximately 2 months, after 12
months of riluzole treatment. This represents a 9% gain in
the probability of surviving for one year (57% in the placebo
and 66% in the riluzole group) [625097]. Despite the
prolongation of survival, there is no clear clinical evidence of
slowing of functional decline, and the basis of the prolonged
survival is uncertain. Riluzole has not been demonstrated to
alter the rate of disease progression or preserve muscle
strength [636040].
AEOL-10150 has progressed through a series of preclinical
studies in models representing a range of diseases, including
ALS, spinal cord injury, islet-cell transplantation for
diabetes, cancer and stroke. The demonstration of a
beneficial effect of AEOL-10150 on survival and delayed
disease progression in the SOD1 mutant mouse model of
ALS led to phase I studies in patients with ALS, and phase
II/III studies in ALS have also been proposed, together with
plans for clinical studies in stroke and radiation-induced
mucositis.
Synthesis and SAR
Metalloporphyrins are low-molecular-weight complexes
that have antioxidant scavenging properties for superoxide,
peroxynitrite and lipid peroxyl radicals. They are water
soluble, manganese meso-porphyrins that are stable and nontoxic
[616369]. Aeolus synthesized AEOL-10150 as a cationic
manganese porphyrin, manganese(III) mesotetrakis(N,N'diethylimidazolium-2-yl)porphyrin
[625100], which can be
abbreviated as Mn IIITDE-2-ImP 5+ [554429]. According to
Batinic-Haberle et al [625100], AEOL-10150 has been
erroneously referred to in a number of publications as
[5,10,l5,20-tetrakis(1,3-diethylimidazolium-2-yl)porphyrinato]
manganese(III) pentachloride [616156], manganese(III)
mesotetrakis (di-N-ethylimidazole) porphyrin [616360], and
manganese(III)meso-tetrakis(N,N'-diethyl-1,3-imidazolium-
2-yl) porphyrin [616370]. In these cases the '1' and '3'
indicated the imidazolyl nitrogens, rather than position 2
where the imidazolyl is attached to the porphyrin ring
[625100].
AEOL-10150 was produced alongside AEOL-10113, the
other lead compound from Aeolus' catalytic antioxidants
pipeline [465629]. AEOL-10113 (manganese (III) tetrakis (Nethylpyridinium-2-yl)
porphyrin or MnTE-2-PyP 5+) is
composed of several stereoisomers, making a pharmaceutically
acceptable formulation difficult to achieve and limiting the
ability to analyze tissue levels and perform pharmacokinetic
studies. AEOL-10113 and related compounds were
synthesized through β-chlorination of 5,10,15,20-tetrakis (2pyridyl)
porphyrin (H2T-2-PyP) followed by N-ethylation
and metallation [625109]. In contrast, AEOL-10150 is a
structurally different metalloporphyrin catalytic antioxidant,
with imidazole side chain substitutions. AEOL-10150 does
not exist as a stereoisomer, is relatively easy to synthesize,
and can be readily analyzed in tissues [465629].
AEOL-10150 was synthesized on the basis of the structureactivity
relationships of AEOL-10113. The metal-centered
redox potential and electrostatics of these compounds have a
key effect on the ability to dismutase superoxides [625100].
AEOL-10150 Orrell 71
AEOL-10150 had a metal-centered redox potential (E1/2)
value of +346 mV, and a catalytic rate constant (log kcat) of
7.83. AEOL-10113 has cationic ortho-N-ethylpyridyl groups
on the methine bridge carbons of the porphyrin ring system
that provides electrostatic guidance for superoxide. The nonplanarity
diminishes the interaction of AEOL-10113 with
DNA and hence reduces the in vivo toxicity of the compound
[413580]. AEOL-10150 has ethyl chains in substitution for
both the ortho-imidazolyl nitrogens of AEOL-10113. This
delocalizes the positive charge over both nitrogens,
providing greater proximity to the mesoporphyrin carbons,
and creates a stronger electron-withdrawing effect than the
positively charged ortho-pyridyl nitrogens [625100].
Separation and detection of these compounds has been
described by high-performance liquid chromatography, with
electrochemical detection apparently offering greater
quantitative sensitivity than spectrophotometric detection,
although less specificity for in vivo applications [625112].
Preclinical development
Mechanism
AEOL-10150 can catalytically decompose biological
oxidants, such as peroxynitrite, by its ability to cycle
between Mn(II) and Mn(IV) states [616156]. The compound
has a +5 charge, with SOD activity between 5000 and 8500
units/g and catalase activity equivalent to approximately
1% of purified bovine catalase (weight/
weight basis) [616360], [616369].
Alternative mechanisms of action have been proposed for
the metallophorphyrins, including neuroprotective effects
mediated by suppression of oxygen-glucose deprivation
(OGD) or N-methyl-D-aspartate (NMDA)-induced rises in
intracellular Ca 2+ concentration [634340], induction of antiapoptotic
protein synthesis [634341], and inhibition of lipid
peroxidation [634325]. However, to date, studies of
AEOL-10150 have focused on antioxidant mechanisms, and
the possibility of other mechanisms remains undefined.
ALS
The effects of AEOL-10150 were demonstrated in mice that
overexpress the human Cu/Zn SOD1 mutant G93A, which
develop a progressive motor neuron disease; this is
currently considered the best animal model of ALS [505222],
[616156]. Three studies were performed and described in a
single paper [616156]. In the first study, AEOL-10150 (5
mg/kg) was administered intraperitoneally as a loading
dose after the first day of symptom onset, followed by daily
maintenance doses of 2.5 mg/kg. A second study
used a similar regime and administered intraperitoneal
AEOL-10150 (2.5 mg/kg) every day following the onset of
symptoms; in addition, creatine and the selective COX-2
inhibitor rofecoxib were also administered (at 2 and 0.005%
in the diet, respectively). The third experiment tested the
same dose of AEOL-10150 (2.5 mg/kg/day) via
subcutaneous administration. The survival interval was
calculated from the onset of symptoms (typically around 90
days of age) until sacrifice at a predetermined late stage of
disease. After calculating the survival interval of treated
mice relative to saline-treated controls (the increased
survival resulting from treatment), a survival interval ratio

72 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
was determined. The mean survival intervals for G93A mice
treated with intraperitoneal AEOL-10150 (2.5 mg/kg/day)
intraperitoneal AEOL-10150 (2.5 mg/kg/day) plus
creatine and rofecoxib, and subcutaneous AEOL-10150
(2.5 mg/kg/day) were 40.0, 38.8 and 40.5 days, respectively,
in the first study; survival ratios in the same groups were
2.96, 2.87 and 2.43, respectively [616156].
Specific deficits were absent in the AEOL-10150-treated
mice, with an absence of hind-limb paralysis until a late
stage compared with control mice. The relative infrequency
of hind-limb paralysis in AEOL-10150-treated mice
compared with complete hind-limb paralysis in almost all
control mice suggests that AEOL-10150 alters the course of
the disease and helps to maintain overall motor function
during the period of extended survival [616156]. These
effects correlate with the preservation of spinal motor
neurons. Neuron counts in the spinal cord demonstrated
increased cellular survival, with 53% of spinal cord neurons
surviving at 100 days in AEOL-10150-treated mice compared
with 38% in untreated mice. Immunostaining for glial
fibrillary acidic protein was reduced in treated mice,
suggesting that gliosis or neuronal injury is reduced. Levels
of protein-bound nitrotyrosine (a marker of oxidative injury)
and malondialdehyde (a marker of lipid oxidation) were
reduced in AEOL-10150-treated G93A mice [616156].
In a follow-up study, AEOL-10150 was tested both as a
single agent and in combination with the histone deacetylase
inhibitor phenylbutyrone in a murine G93A SOD1
transgenic model [633859]. The neurodegenerative effects of
phenylbutyrate (400 mg/kg/day) and phenylbutyrate (400
mg/kg/day) combined with AEOL-10150 (2.5 mg/kg/day)
were compared with a control. Treatments were
administered intraperitoneally, commencing at disease onset
(between 85 and 92 days of age). In mice treated with
AEOL-10150 alone there was a significant increase in
survival, from 132 ± 5 to 146 ± 15 days (11%). Mice
administered with phenylbutyrone alone showed an
increase in survival from 126 ± 4 to 143 ± 9 days (13%).
When AEOL-10150 was administered together with
phenylbutyrone, survival increased to 150 ± 13 days (19%).
The combination therapy was significantly more effective
than phenylbutyrone alone (p < 0.05). Motor performance in
mice treated with AEOL-10150 alone was not significantly
increased, whereas mice treated with phenylbutyrone, both
alone and in combination with AEOL-10150, showed a
significantly improved motor performance compared with
control. Loss of motor neurons in the lumbar spinal cord
was assessed histologically and was significantly reduced
with all treatment combinations. Immunohistochemical
analysis of malondialdehyde and 3-nitrotyrosine, thought to
be relatively specific markers of oxidative damage, showed
increased expression in control mice, and a marked
reduction at 115 days in all other treatment groups [633859].
The mechanism of action of AEOL-10150 in G93A mice is
unlikely to be due to SOD-like activity, as these mice
overexpress SOD. Prevention of the formation of proteinbound
nitrotyrosine and malondialdehyde suggests an
antioxidant effect on the preservation of spinal motor
neurons [616156]. As it is currently unknown whether the
best possible survival effects have been achieved, further
studies to rigorously examine dose, route and frequency of
administration of AEOL-10150 in ALS models are ongoing.
Spinal cord injury
C57BL/6J mice were subjected to spinal cord compression
for 60 min at the T11 vertebral level. In the first experiment
of a two-part study, AEOL-10150 was administered as a 0.5mg/kg
bolus dose, followed by a 1.0 mg/kg intravenous
infusion every hour for 24 h, beginning 5 min after onset of
spinal cord compression (n = 25). In the second experiment,
AEOL-10150 was administered as an intrathecal injection
(2.5 or 5.0 µg/kg; total n = 18). Rotarod performance
demonstrated that intrathecal administration of 5 µg of
AEOL-10150 was associated with an approximately 30%
improvement in neurological behavior (p < 0.05), and a
reduction was observed in histological total damage score
(19 ± 8; p = 0.03) compared with controls (26 ± 10).
Intravenous administration of AEOL-10150 produced no
significant changes in these tests compared with controls
[554429], [616364].
Stroke
AEOL-10150 was administered in a C57BL/6J mouse model
of stroke [616369]. Mice were subjected to transient (60 min)
middle cerebral artery occlusion (MCAO; n = 6) or sham
surgery (n = 6), and were then treated with AEOL-10150 5
min after reperfusion. A bolus dose of AEOL-10150 (0.5
mg/kg) was followed by continuous intravenous infusion of
1.0 mg/kg/h for 6 h. At this time, the brains were studied
and mRNA expression was analyzed using an Affymetrix
murine microarray. AEOL-10150 attenuated the injuryinduced
increase in expression of pro-inflammatory cytokine
genes. For example, MCAO caused a 12-fold upregulation in
macrophage inflammatory protein (MIP)-2 in untreated
animals, compared with a 6-fold increase following
AEOL-10150 treatment. However, AEOL-10150 had no
apparent effect on the expression of stress response genes,
suggesting that the protective effect of the drug may be
independent of any stress response pathways. A possible
explanation is that AEOL-10150 is compartmentalized to the
extracellular space because of its +5 charge, and therefore
produces no effect on the stress response genes, which are
regulated by intracellular events. However, studies with a
range of manganese porphyrins, including AEOL-10113
(which also has a +5 charge), indicated that they penetrated
mitochondrial and cytosolic fractions of cortical cells in
concentrations sufficient for antioxidant activity [634343].
Slight changes were observed in the expression of
antioxidant genes, including glutathionine transferase,
neuronal nitric oxide synthase, Cu/Zn SOD, extracellular
SOD and mitochondrial SOD. No significant changes were
recorded in the expression of apoptosis and growth factor
genes, suggesting that AEOL-10150 has no effect on these
pathways [616369].
In a study in rats, AEOL-10150 and AEOL-10113 were
administered intracerebroventricularly 90 min after a 90-min
MCAO [465629]. Dose escalation was performed, in which
the initial 300-ng dose of AEOL-10150 was doubled until

side effects were observed. The maximal dose of
AEOL-10150 in rats that was clearly devoid of adverse
behavioral effects was 4500 ng. AEOL-10113 caused
behavioral side effects at twice the neuroprotective dose, but
AEOL-10150 caused similar changes at 15-fold the
neuroprotective dose [413580]. AEOL-10150 and
AEOL-10113 reduced infarct size by 35% when administered
90 min after occlusion. When AEOL-10150 was administered
6 h after occlusion, infarct size was reduced by 43% [465629].
In a similar study, AEOL-10150 reduced infarct size by 40%,
but with no associated functional improvement [468211].
AEOL-10113 was not reported at 6 h, but in previous
experiments a 54% reduction in infarct volume was
reported, together with a reduction in neurological deficit
[413580]. In another study, using the same dosing schedule
in mice, neuroprotective effects were observed in brain
parenchymal protein expression where AEOL-10150
inhibited changes in protein expression that were
attributable to MCAO [428437].
A comparable study of intravenous AEOL-10150 was
conducted in a murine model [465629]. A similar doseescalation
design was implemented in two cohorts,
following either MCAO or sham surgery, followed by an
intravenous bolus dose of 0.5 mg/kg AEOL-10150 and a
continuous intravenous infusion at 1.0 mg/kg/h for 24 h
(n = 6/group). A 25% reduction in infarct size and a
reduction in neurological deficit were demonstrated
[465629]. Uptake of AEOL-10150 into the brain was slow,
dose- and time-dependent and greater in the ischemic
hemisphere. AEOL-10150 had direct effects on brain
parenchymal protein expression, supporting the hypothesis
that a potent catalytic antioxidant can independently cause
diverse changes in protein expression and ameliorate
changes induced by ischemic insult [465629].
One further in vitro study by Sheng et al examined the ability of
AEOL-10150 to reduce cell death in conditions of oxidative
stress [465629]. Neuronal and glial cell cultures were prepared
from embryonic (day 18) rat cerebral hemispheres, and
AEOL-10150 was applied to the assays 30 min prior to
placement in oxygen/glucose deprivation (OGD). AEOL-10150
inhibited cell death in a concentration-dependent manner (p <
0.0001) following OGD. The optimal effect of the drug occurred
at 10 µM, at which 48% of the OGD-induced lactate
dehydrogenase release was inhibited. AEOL-10150 selectively
inhibited aconitase inactivation (measured 8 h after OGD)
[465629]. The preservation of aconitase activity is used as a
marker of specific inhibition of superoxide-mediated injury
[638331].
Transplantation
In human pancreatic islet-cell allotransplantation, a
treatment being developed for diabetes mellitus, the
mechanical and chemical insults caused to transplanted cells
by oxidative stresses significantly reduce their viability and
function. In an experiment by Bottino et al, AEOL-10150 was
added to the culture medium of purified human islet cells,
and also at the isolation phase [463528]. After 24 h, there was
a 3-fold increase in the mass of AEOL-10150-treated cells
compared with untreated control cells. When transplanted
AEOL-10150 Orrell 73
to diabetic mice, glucose levels were normalized in nine of
nine mice receiving AEOL-10150-treated islet cell cultures,
but only five of eight animals receiving untreated cells. The
in vitro glucose responsiveness and in vivo function of the
cells that survived demonstrated that AEOL-10150 does not
impair islet functional performance. AEOL-10150 seemed to
protect the human islets from oxidative and free radical
stresses, improving the preservation of the isolated tissue,
suggesting that the drug may be usefully applied to the
procurement solution during organ perfusion to obtain a
more successful protective effect before transplant [463528].
Pancreatic islet β-cells are reported to be highly susceptible
to oxidative stress because of reduced endogenous
antioxidant levels [632736]. Under conditions of extreme
stress, for example, islet-cell isolation procedures following
clinical transplantation, the antioxidant defenses of the βcells
may be overwhelmed, which may lead to a state of
redox imbalance and the production of reactive oxygen
species (ROS). A potential ROS-dependent target is nuclear
factor (NF)κB. In a second study, Bottino et al demonstrated
that AEOL-10150 reduced the level of NFκB in treated islet
β-cells, correlating with reduced production of cytokines
and chemokines, and reduced activation of apoptosis and
necrosis, further supporting the use of AEOL-10150 in the
protection of pancreatic islet cells used for transplantation
treatment of diabetes [632736].
Hemorrhage-induced lung injury
The effect of hemorrhage-induced lung injury was studied
in extracellular (EC)-SOD knockout mice, with and without
pre-treatment with a single subcutaneous dose of
AEOL-10150 (24 mg/kg) [616360]. Compared with wild-type
mice, EC-SOD-deficient mice had increased lung neutrophil
accumulation, a 3.9-fold increase in myeloperoxidase
activity, a 1.5-fold increase in NFκB activation, and a 1.5-fold
increase in lipid peroxidation 1 h after hemorrhage. Pretreatment
with AEOL-10150 did not attenuate neutrophil
accumulation in the lungs, but reduced NFκB activation and
isoprostane formation in both wild-type and EC-SODdeficient
mice. However, the beneficial effects of
AEOL-10150 were moderate and no reduction in neutrophil
recruitment to the lungs was observed, suggesting that
AEOL-10150 can attenuate markers of oxidative stress, but
may not reduce lung injury as measured by neutrophil
accumulation [616360].
Radiation-induced lung injury
The effects of radiation-induced injury were examined in 344
Fisher rats. Following the administration of a single
irradiation dose (26 Gy) to the right hemithorax, rats were
treated with AEOL-10150 (1, 10 or 30 mg/kg/day) for 10
weeks, via a subcutaneous osmotic pump. Follow-up
examinations at 20 weeks showed significantly improved
breathing rates in both the 10 and 30 mg/kg/day groups. In
the same two groups, a reduction in oxidative stress (as
measured by levels of 8-hydroxydeoxyguanosine; 8OHdG),
a reduction in macrophage levels and a significant decrease
in structural disease were observed, compared with the
control and 1-mg/kg/day groups. The doses and route of
administration used in this study were implemented into a

74 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
phase I study of AEOL-10150 in ALS patients [629090],
[638411].
Tobacco-smoke-induced lung inflammation
Cigarette smokers experience airway inflammation and
epithelial damage, which is thought to be caused by the
formation of free radicals by chemicals in the smoke, leading
to oxidative stress. AEOL-10150 (either 5 mg/kg
administered approximately 2 h before a 2-day toxicity
study, or as eight weekly doses of 2 mg/kg in a long-term
toxicity model) was administered by intratracheal
instillation to rats exposed to filtered air or tobacco smoke
[616370], [616377]. A lower dose was used for the 8-week
study in order to minimize potential long-term toxicity.
AEOL-10150 significantly reduced bronchoalveolar lavage
cell numbers in tobacco-smoke-treated rats, with reductions
in counts of neutrophils, macrophages and lymphocytes at
different time points. Squamous cell metaplasia was reduced
from 12% of total airway epithelial area to 2% after 8 weeks
of treatment with AEOL-10150. AEOL-10150 was also
observed to attenuate decreases in levels of MIP-2 and
intracellular adhesion molecule-1, important proteins in the
migration and presentation of neutrophils and
macrophages. The expression of these two proteins is
mediated by NFκB and, therefore, it was suggested
that AEOL-10150 decreases tobacco-smoke-induced
inflammation in the lungs of rats by reducing oxidative
stress and the resultant activation of NFκB [616370].
Autoimmune disease
The effect of AEOL-10150 (and AEOL-10113) on
lipopolysaccharide-stimulated macrophages was studied to
determine the role of oxidation-reduction reactions in the
activation of the immune system. In the presence of
AEOL-10150, the cells failed to elicit a pro-inflammatory
response, and levels of the pro-inflammatory cytokines tumor
necrosis factor α and interleukin-1β were decreased. There was
also a reduced ability to generate reactive oxygen species, with
decreased superoxide and peroxynitrite production. These
effects led to the inhibition of the NFκB pathway at the DNA
binding level, which, if mediated by the catalytic antioxidant
inhibition, suggests that this pathway is dependent on the
redox state within the cell. This finding implies that immune
activation might not be an on/off response, but one that is
mediated to some degree by free-radical signaling. The
potential of AEOL-10150 to suppress this immune response
suggests long-term applications in preventing the activation of
the adaptive immune response in organ-specific autoimmune
diseases in which chronic inflammation causes delayed-type
hypersensitivity and tissue destruction [616358].
Mucositis
AEOL-10150 was reported to reduce the incidence and
duration of radiation-induced oral mucositis in a hamster
model [432294]. Intraperitoneal (0.05, 0.2 and 0.3 mg/ml) or
topical (0.05, 0.2, 0.3 and 1.0 mg/ml) AEOL-10150 was
administered three-times daily for 20 days, commencing a
day before a single 40 Gy dose of radiation. Relative to
vehicle-treated control animals, intraperitoneal AEOL-10150
reduced the number of days of severe mucositis (ulceration)
by 35 to 59% at all doses, and topical administration (of 1.0
mg/ml) reduced the number of days by 36%. The drug also
protected against conditions that commonly arise in association
with oxidative free radical damage, reducing mitochondrial
aconitase inactivation (by 4-fold with topical administration
and 2.5-fold with intraperitoneal administration) and 8OHdG
formation (by 1.5-fold following either topical or intraperitoneal
administration) [432294]. These data have been presented in
abstract form only, with no indication of dosing based on
weight. Total daily doses were equivalent to 0.03, 0.12, 0.18 and
0.6 mg/day [432294].
Cancer
A more recent study examined the effect of AEOL-10150 on
the efficacy and toxicity of anticancer radiation therapy
[595706]. Male C57BL/6 mice were injected subcutaneously
with RM9 prostate tumor cells before being treated with
intraperitoneal AEOL-10150 (6 mg/kg) for 16 days.
Radiation (10 Gy) was delivered on day 8. Three days after
the application of irradiation, hematological analysis
showed that radiation alone significantly slowed tumor
progression (p ≤ 0.05) and that a slight antitumor response
was observed with AEOL-10150 treatment alone. The most
potent effect was observed when AEOL-10150 was
combined with radiation, after which tumor volumes were
significantly reduced on days 8 and 10 to 14, compared with
untreated controls. It was also suggested that AEOL-10150
increased the efficacy of radiation because smaller tumor
volumes were recorded on days 10, 13 and 16 in the
AEOL-10150 plus radiation group than in animals receiving
radiation alone (p ≤ 0.05). Recordings of body mass were
similar among all groups during the majority of the study.
These findings support the utilization of AEOL-10150 as a
possible therapy in slowing tumor progression and suggest
that greater tumor control may be possible when the
compound is combined with radiation [595706].
Metabolism and pharmacokinetics
Pharmacokinetic parameters were determined in a rat study
of AEOL-10150 (300 ng) injected intracerebroventricularly 90
min after reperfusion from MCAO [465629]. No compound
was detected in the liver. Plasma concentrations were
generally negligible, but reached levels of 4.6 and 3.2 ng/ml
in two rats. Brain parenchymal AEOL-10150 peaked within 1
h of injection, and the tissue half-life was calculated to be
approximately 10 h [465629].
In a mouse model of MCAO and reperfusion, AEOL-10150
was administered as an intravenous bolus of 2.5 mg/kg,
followed by infusion of 1 mg/kg/h. The plasma
concentration of AEOL-10150 was stable at 3 to 4 µg/ml. The
drug concentration in both ipsilateral and contralateral brain
regions increased with time, but was 2- to 4-fold greater in
the ischemic hemisphere [468211].
Modeling based on animal and human data predicted the
efficacious dose of AEOL-10150 in humans with ALS to be
approximately 12 mg daily. It therefore appears that a wide
therapeutic window exists for AEOL-10150, according to
current safety data and dose-linear pharmacokinetics in animals
and humans [616116].
A multicenter, double-blind, randomized, placebo-controlled,
escalating-dose study of subcutaneously administered single
doses of AEOL-10150 (3, 12, 30, 45, 60 and 75 mg) to 25 patients

(n = 3 or 4 per cohort) has been conducted [621716].
Pharmacokinetic data from the study showed that responses
were dose-dependent, AUC values ranging from 354 to 12,167
ng.h/ml (following 3- and 75-mg doses). Cmax values ranged
from 114.8 to 1584 ng/ml, Tmax values ranged from 1 to 2 h and
mean half-life values from 2.6 to 6.4 h (3 and 75 mg) [621716].
Toxicity
A study in rats compared the relative behavioral neurotoxicity
of AEOL-10113 and AEOL-10150 [465629]. Animals were
examined for 2 h after injection, and if no adverse behavioral
responses were observed the dose was doubled in a new set of
rats. In animals treated with AEOL-10113, a behavioral
syndrome with sustained proptosis (a protuberance of the
eyeball out of its socket), ataxia (impaired muscle function or
movement) and hypersensitivity to sound was observed. For
AEOL-10113, an intracerebroventricular dose of 600 ng was
reached before minor behavioral side effects became noticeable
compared with 9 µg for AEOL-10150, a 15-fold reduction in
toxicity. No effect of the drugs on body temperature was
detected [465629].
When administered to mice for 16 days, alone or in
combination with radiation, AEOL-10150 (6 mg/kg/day)
did not produce any detectable toxicities affecting body
mass, behavior or hematological analyses [595706].
In male Wistar rats, intravenous AEOL-10150 in doses of
> 0.1 mg/kg produced a reduction of mean arterial pressure
of > 20%. The duration of hypotension was dose dependent,
with 0.5 mg/kg causing irreversible profound hypotension,
but smaller doses producing only transient effects. No
change in mean arterial pressure was observed when an
intracerebroventricular route was used [465629].
In a murine prostate cancer model, animals treated with
AEOL-10150 (6 mg/kg) for 16 days had a significantly elevated
white blood cell count due to granulocytosis (p ≤ 0.05) [595706].
Levels of red blood cells and platelets, hemoglobin and
hematocrit were similar among groups tested. A trend of
elevated white blood cells was observed in the spleens of mice
treated with AEOL-10150 (p < 0.1), with increases in both
granulocytes and macrophages (p < 0.05). Additional studies
are needed to understand the biological significance, if any, of
the increased white blood cell counts [595706].
Clinical development
Phase I
A multicenter, double-blind, randomized, placebo-controlled
study evaluated escalating, subcutaneous single doses of
AEOL-10150 (3, 12, 30, 45, 60 and 75 mg) in 25 ALS patients
[592224], [621716]. Recently reported pharmacokinetic data
from the trial are detailed above, and side effects/
tolerability detailed in the side effects and contraindications
section below.
A second multicenter, multiple-dose study was expected to
enroll 18 ALS patients to receive subcutaneous injections of
40, 60 or 75 mg of AEOL-10150 (n = 4/dose) or placebo
(n = 6), twice daily for 6 days, with a single injection on the
seventh day. The trial was to collect efficacy, safety and
AEOL-10150 Orrell 75
pharmacokinetic data, and was expected to be completed by
the end of 2005 or early in 2006 [629382].
Aeolus has announced plans to initiate trials in other
indications. In February 2005, the company was to file an
investigational new drug application prior to initiating a
phase I study of AEOL-10150 in radiation-induced mucositis
[583926].
The company had announced in April 2004 that, depending
on the results of phase I trials in ALS, a pivotal phase II/III
trial in this indication could be initiated by the first half of
2005 [533629]. In February 2005, the company stated its
intention to initiate an efficacy study of AEOL-10150 in
stroke patients [583926]. At the time of publication, however,
no further details of these studies were available.
Side effects and contraindications
The most common side effects that have been reported
from phase I trials of ALS patients were injection-site
reactions, dizziness and headache [592224]. The adverse
events were considered mild in severity, and
approximately 50% of these events were possibly related
to the study medication. No serious adverse events,
laboratory abnormalities or cardiovascular issues were
observed [621716]. Initial observations from the multipledose
study in ALS patients have demonstrated no serious
adverse events [629382].
Single doses of AEOL-10150 ranging from 3 to 30 mg were
well tolerated [592224], and no serious adverse events were
reported. No clinically meaningful abnormalities were noted
in safety laboratory tests, vital signs, unified Parkinson's
disease rating scale, functional ALS assessments or
electrocardiogram data. Further studies of up to 75 mg of
AEOL-10150 in humans revealed no serious adverse events
or laboratory abnormalities [616116].
Patent summary
WO-09510185, published in April 1995 by Duke University and
the University of Melbourne Research Foundation, describes
novel mimetics of SOD and inhibitors of xanthine. Claims are
made for various manganic derivatives of methine-substituted
porphyrins, prepared by conventional methods, including the
products AEOL-10113 and AEOL-10150. In December 1996, the
University of Alabama Research Foundation and Duke
University published WO-09640223, describing the modulation
of intra- or extracellular levels of oxidants, such as superoxide
radicals, hydrogen peroxides and peroxynitrite; potential was
claimed in the therapy of ischemia, myocardial infarction,
reperfusion injury, and inflammatory disorders, such as asthma
and rheumatoid arthritis.
In July 2000, AEOL-10150 was first claimed in WO-00043395,
which is expected to be granted as EP-01155019 in December
2005, describing the modulation of cellular levels of oxidants
using substituted porphyrins. AEOL-10150 is specifically
claimed in US-06544975. Both the European and US cases are in
the name of the National Jewish Medical & Research Center,
Aeolus Pharmaceuticals Inc and Duke University. AEOL-10150
should have solid patent protection at least until January 2020.

76 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Further patents associated with the drug include WO-02060383
(published in August 2002), which claims the use of a list of
SOD mimetics, including AEOL-10150, for treating cancer, and
WO-02098431 (published in December 2002), which specifically
claims AEOL-10150 for the treatment of diabetes.
Current opinion
Oxidative stress and free-radical-mediated damage have
been implicated in a broad range of diseases. Many of these
diseases, namely stroke, myocardial infarction, cancer, and
neurodegenerative and inflammatory diseases, are common,
especially in later life, and cause significant disability as a
result of the tissue damage. In particular, if free-radicalmediated
damage can be diminished or halted after the
immediate insult, for example, in stroke or myocardial
infarction, there is the prospect of significantly improving
survival and reducing disability. Nevertheless, to date, the
results of clinical studies of other antioxidant (eg, vitamins C
and E, selegiline and N-acetylcysteine) and neuroprotective
compounds (eg, β-lactam antibiotics and minocycline) have
been largely disappointing [625121], [638229]. This may be a
consequence of the animal and tissue models used, and the
difficulty in applying the therapeutic interventions
sufficiently early in clinical practice. The lack of efficacy may
also relate to the compounds being inappropriate.
Questions remain as to the mechanism of action of
metalloporphyrins, including AEOL-10150. The therapeutic
mechanism may not be their antioxidant properties, and more
studies should be conducted in preclinical models to determine
alternative mechanisms, studying markers other than those of
oxidative stress. For example, heat shock proteins are also
implicated in the pathogenesis of ALS, and their modulation
has produced some benefit in preclinical studies [634318],
[634320]. This finding may have significant implications for
targeting diseases, and determining the most effective
compound for further studies. Also, the free-radical-scavenging
ability of the metalloporphyrins may be reduced or abolished
by structural modifications. Including such modified
compounds as controls in studies of AEOL-10150 is important
to clarify the therapeutic mechanisms.
SOD mimetics and similar compounds that affect free radicals
and oxidative stress have the potential for clinical efficacy.
AEOL-10150 was apparently tolerated in phase I studies, and
has the advantage of being subcutaneously administered. For
treatment of a chronic disease process, such as ALS, where
oxidative damage is presumed to be ongoing throughout the
disease, treatment would presumably require regular
administration of the compound and access to the central
nervous system. ALS would appear to be a sensible choice of
disease in which to study the clinical effects of AEOL-10150
because of the presumption of oxidative stress as a component
of the pathology, and also because the rapid progression of the
disease allows clinical efficacy to be studied in a relatively short
time period. ALS is a serious and fatal disease in urgent need of
effective treatment. A range of antioxidants have been
evaluated in the treatment of this disorder, with no proven
efficacy [625121], but these have usually been of low potency
and specificity, and evaluated in poorly designed studies. The
only current licensed medication for ALS, riluzole, has only
slight efficacy [625097], [625122], and there is the expectation
that other medications will have a more significant effect in the
future, either alone or in combination with riluzole and other
compounds. The observation of an additive therapeutic effect of
AEOL-10150 when combined with sodium phenylbutyrate
supports this view [633859], and is important when designing
preclinical and clinical studies, and determining the eventual
utility of the compound.
Some caution is needed in the interpretation of therapeutic
studies in SOD1 transgenic mice, as a range of compounds have
been demonstrated to have efficacy on survival, but this efficacy
has not been translated to effects in humans [638229]. Also, a
range of different SOD1 transgenic mouse models exist, with
different mutations, different expression loads and different
background survival, making comparison of survival times or
efficacy difficult. An important study in a mouse model would
be to examine a combination of riluzole and AEOL-10150,
comparing the combination with the effects on animals treated
with the individual agents and placebo. It is probable that any
clinical trial in humans with ALS will require the patients to be
taking riluzole as well as AEOL-10150, for ethical reasons. A
criticism that may be raised concerning the treatment of
degenerative conditions, such as ALS (and other conditions
such as cancer, stroke and heart disease), is that in prolonging
survival, suffering or disability may also be prolonged. Hence,
the observation that mice treated with AEOL-10150 retained
their ability to walk on all four limbs and perform other normal
activities throughout the extended period of survival, rather
than experience a gradual deterioration or prolongation of
lifespan in significant physical disability, is potentially
important [616116], [616156].
More effective antioxidants are also being synthesized, for
example, through the modification of AEOL-10150 by including
oxygen atoms [625100]. Three new Mn(III) porphyrin SOD-like
catalysts, with ether oxygen atoms in the side chains, have been
synthesized and characterized by the same laboratory [625100].
When compared with AEOL-10113 and AEOL-10150,
MnTDMOE-2-ImP 5+ (where all eight ethyl groups are replaced
by methoxyethyl groups) was the most effective catalyst of
SOD, while AEOL-10150 was stated to be of low efficacy
[625100]. Comparative studies of these antioxidants in the G93A
SOD1 mutant mouse would be of interest because it is the best
available ALS model. In one study, the synthetic superoxide
dismutase/catalase mimetics (salen manganese complexes),
EUK-8 and EUK-134 (Proteome Systems Ltd) were
administered intraperitoneally to low-expressing G93A mice,
110 days before onset. Disease onset occurs later in these mice
(170 days), and prolongation of up to 6 days occurs in the
EUK-8-treated group, a 1.1-fold increase in total life span. Using
the survival interval ratio, values of 1.2-fold for EUK-8 and
1.6-fold for EUK-134 were calculated [625120]. In another
study, iron porphyrin (FeTCPP) 5,10,15,20-tetrakis-4carboxyphenylporphyrin
was administered to G93A SOD1
mutant mice. The mean survival time was increased by 7 days
in treated mice compared with controls [625101].
If clinical efficacy of AEOL-10150 is demonstrated in any one
of the proposed treatment indications, the possibilities of
efficacy in the remaining indications would appear to be good.

Although subcutaneous administration is of benefit for chronic
conditions, intravenous administration with access to
appropriate tissues, especially brain in stroke and spinal cord in
trauma, is important. The recurrent problem in treating these
acute conditions is diagnosing and administering the
medication within the first few hours of the insult.
Development history
AEOL-10150 Orrell 77
Preclinical trials of AEOL-10150 have shown promise of
efficacy in a range of diseases that cause significant
mortality, disability and suffering. However, the
mechanisms of action and relative efficacy of
AEOL-10150 and other metalloporphyrins require further
study.
Developer Country Status Indication Date Reference
Aeolus Pharmaceuticals Inc US Phase I Motor neuron disease 31-OCT-04 583926
Aeolus Pharmaceuticals Inc US Discovery Cerebrovascular ischemia 24-NOV-00 391004
Aeolus Pharmaceuticals Inc US Discovery Lung inflammation 01-AUG-01 616377
Aeolus Pharmaceuticals Inc US Discovery Mucositis 01-OCT-01 432294
Aeolus Pharmaceuticals Inc US Discovery Spinal cord injury 04-MAR-04 554429
Literature classifications
Chemistry
Study type Result Reference
SAR. A number of related manganese (III) compounds were studied and compared. AEOL-10150, a stable
and non-toxic manganese mesoporphyrin, was selected on the basis of its redox potentials (E1/2 value
of +346 mV and log kcat value of 7.83).
625100
Biology
Study type Effect studied Model Result Reference
In vitro Efficacy. AEOL-10150 was added during the After 24 h, there was a 3-fold increase in 463528
isolation and culture of purified human the mass of AEOL-10150-treated cells
pancreatic islet cells.
compared with untreated cells. When
transplanted to diabetic mice, glucose
levels were normalized in nine out of nine
mice receiving AEOL-10150-treated isletcell
cultures but in only five out of eight
animals receiving untreated cells.
In vivo Efficacy. SOD1-overexpressing G93A mice Compared with placebo, the mean
616156
administered one of three schedules increases in survival for mice treated with
(5 mg/kg AEOL-10150
intraperitoneal AEOL-10150,
intraperitoneally as a loading dose intraperitoneal AEOL-10150 plus creatine
followed by daily maintenance doses and rofecoxib, and subcutaneous
of 2.5 mg/kg; 2.5 mg/kg AEOL-10150 AEOL-10150 were 40.0, 38.8 and 40.5
intraperitoneally with creatine and days, respectively; survival ratios in the
rofecoxib (2 and 0.005% in diet, same groups were 2.96, 2.87 and 2.43,
respectively); or 2.5 mg/kg/day
AEOL-10150 via subcutaneous
administration) were treated from the
first day of symptom onset
(~ 90 days of age).
respectively.
In vivo Efficacy. SOD1-overexpressing G93A mice Compared with placebo, the mean
633859
administered one of three dosing survival of mice treated with AEOL-10150
schedules intraperitoneally
alone, with phenylbutyrate alone, and with
(AEOL-10150 (2.5 mg/kg/day), the combination of AEOL-10150 and
phenylbutyrate (400 mg/kg/day), and phenylbutyrate increased by 11, 13 and
a combination of AEOL-10150
and phenylbutyrate at the same
doses). Animals were treated from the
first day of symptom onset (~ 90 days
of age).
19%, respectively.
In vivo Efficacy. C57BL/6J mice (n = 18) subjected to Rotarod performance demonstrated that 554429
spinal cord compression for 60 min, intrathecal administration of AEOL-10150
with AEOL-10150 or placebo
was associated with ~ 30% improvement
administered 5 min later. In two in neurological behavior (p < 0.05), and a
studies, AEOL-10150 was
reduction was seen in histological total
administered as a 0.5-mg/kg bolus damage score (19 ± 8; p = 0.03)
dose followed by a 1.0-mg/kg
intravenous infusion every hour for 24
compared with controls (26 ± 10).
Intravenous administration of
h (n = 25), or as an intrathecal
injection (2.5 or 5.0 µg/kg).
AEOL-10150 showed no significant
changes compared with the control group.

78 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Biology (continued)
Study type Effect studied Model Result Reference
In vivo Efficacy. MCAO or sham surgery in mice A 25% reduction in infarct size and a
465629
(n = 6/group) followed by an
reduction in neurological deficit were
intravenous bolus dose of
AEOL-10150 (0.5 mg/kg) and a
continuous intravenous infusion at
1.0 mg/kg/h for 24 h (n = 6/group).
demonstrated.
Metabolism
Study type Effect studied Model Result Reference
In vivo Pharmacokinetics. AEOL-10150 (300 ng)
The drug was not detected in the liver.
465629
administered
Plasma concentrations were generally
intracerebroventricularly 90 min negligible, but reached 4.6 and 3.2 ng/ml in
after MCAO in rats.
two rats. Brain parenchymal AEOL-10150
peaked within 1 h of injection, and the
tissue half-life was calculated to be ~ 10 h.
In vivo Pharmacokinetics. Post MCAO or sham surgery, mice
received an intravenous bolus
dose of AEOL-10150 (0.5 mg/kg)
and a continuous intravenous
infusion of AEOL-10150 at 1.0
mg/kg/h for 24 h.
In vivo Pharmacokinetics. A phase I, double-blind,
randomized, placebo-controlled,
single escalating-dose study of
subcutaneous AEOL-10150 (3, 12,
30, 45, 60 and 75 mg) in 25 ALS
patients.
Clinical
Uptake of the drug into the brain was slow,
dose- and time- dependent, and greater in
the ischemic hemisphere.
Responses were dose dependent, with AUC
values ranging from 354 to 12,167 ng.h/ml
(following 3- and 75-mg doses, respectively).
Cmax values ranged from 114.8 to 1584 ng/ml,
Tmax ranged from 1 to 2 h, and mean half-lives
from 2.6 to 6.4 h (following doses of 3 and 75
mg, respectively).
465629
621716
Effect studied Model Result Reference
Safety. A phase I, multicenter, double-blind, randomized, No serious adverse effects, laboratory
621716
placebo-controlled, single escalating-dose study of abnormalities or cardiovascular issues were
subcutaneous AEOL-10150 (3, 12, 30, 45, 60 and recorded. The most common adverse effects were
75 mg) in 25 ALS patients.
injection-site reactions, dizziness and headache.
Associated patent
Title Substituted porphyrins.
Assignee National Jewish Medical and Research Center
Publication WO-00043395 27-JUL-00
Priority US-19990117010 25-JAN-99
Inventors Crapo JD, Day BJ, Trova MP, Gauuan PJF, Kitchen DB.
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583926 Aeolus Pharmaceuticals announces first quarter financial
results. Aeolus Pharmaceuticals Inc PRESS RELEASE 2005 February 08
592224 Aeolus Pharmaceuticals Inc announces optimistic AEOL 10150
phase 1 clinical trial interim results in patients with Lou Gehrig's
disease. Aeolus Pharmaceuticals Inc PRESS RELEASE 2005 March 29
595706 Effect of AEOL 10150 on prostate tumor response to radiation.
Makinde AY, Rizvi A, Luo X, Andres ML, Archambeau JO, Pearlstein RD,
Slater JM, Gridley DS PROC AM ASSOC CANCER RES 2005 46 Abs 1991
616116 Aeolus Pharmaceuticals Inc announces publication of results of
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PRESS RELEASE 2005 August 04
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survival of ALS mice. Crow JP, Calingasan NY, Chen J, Hill J, Beal MF ANN
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616358 Mechanistic analysis of the immunomodulatory effects of a
catalytic antioxidant on antigen-presenting cells: Implication for their
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HM, Milton MJ, Piganelli JD FREE RADIC BIOL MED 2004 36 2 233-247
616360 Evidence for extracellular superoxide dismutase as a mediator of
hemorrhage-induced lung injury. Bowler RP, Aracoli J, Abraham E, Patel
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Sheng H, Spasojevic I, Warner DS, Batinic-Haberle I FREE RADIC BIOL
MED 2003 35 Suppl 1 S154
616369 A catalytic antioxidant (AEOL 10150) attenuates expression of
inflammatory genes in stroke. Bowler RP, Sheng H, Enghild JJ, Pearlstein
RD, Warner AS, Crapo JD FREE RADIC BIOL MED 2002 33 8 1141-1152
616370 Inhibition of tobacco smoke-induced lung inflammation by a
catalytic antioxidant. Smith KR, Uyeminami DL, Kodavanti UP, Chang LY,
Crapo JD, Pinkerton KE FREE RADIC BIOL MED 2002 33 8 1106-1114
616377 Attenuation of cigarette smoke-induced lung inflammation and
remodeling by treatment with the metalloporphyrin (AEOL 10150).
Pinkerton KE, Smith KR, Kodavanti U, Chang LY, Crapo JD FREE RADIC
BIOL MED 2001 31 10 S49
621716 Aeolus Pharmaceuticals reports positive safety results from
completed phase I single dose study of AEOL 10150 in 25 patients with
ALS (Lou Gehrig's disease). Aeolus Pharmaceuticals Inc PRESS RELEASE
2005 September 07
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disease (MND). Miller RG, Mitchell JD, Lyon M, Moore DH COCHRANE
DATABASE SYST REV 2001 4 CD001447
625100 New class of potent catalysts of O2 dismutation. Mn(III) orthomethoxyethylpyridyl-
and di-ortho-methoxyethylimidazolylporphyrins.
Batinic-Haberle I, Spasojevic I, Stevens RD, Hambright P, Neta P, Okado-
Matsumoto A, Fridovich I DALTON TRANS 2004 11 1696-1702.
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Beal MF Iron porphyrin treatment extends survival in a transgenic animal
model of amyotrophic lateral sclerosis. J NEUROCHEM 2003 85 1 142-
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625109 Syntheses and superoxide dismuting activities of partially (1-4)
β-chlorinated derivatives of manganese (III) meso-tetrakis (-ethylpyridinium-2-yl)
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625112 High-performance liquid chromatography with
spectrophotometric and electrochemical detection of a series of
manganese (III) cationic porphyrins. Kachadourian R, Menzeleev R, Agha
B, Bocckino SB, Day BJ J CHROMATOGR B ANAL TECHNOL BIOMED LIFE
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Crow JP FREE RADIC BIOL MED 2000 28 10 1487-1494.
625120 Synthetic superoxide dismutase/catalase mimetics reduce
oxidative stress and prolong surival in a mouse amyotrophic lateral
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629090 Protection of normal tissue from radiation-induced injury using
AEOL 10150 presented at the annual meeting of the American Society
for Therapeutic Radiology and Oncology. Aeolus Pharmaceuticals Inc
PRESS RELEASE 2005 October 18
629382 Aeolus Pharmaceuticals announces initiation of multiple dose
study of AEOL 10150 in patients with Lou Gehrig's disease. Aeolus
Pharmaceuticals Inc PRESS RELEASE 2005 October 19
632736 Response of human islets to isolation stress and the effect of
antioxidant treatment. Bottino R, Balamurugan AN, Tse H,
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Piganeli JD DIABETES 2004 53 10 2559-2568
633859 Additive neuroprotective effects of a histone deacetylase
inhibitor and a catalytic antioxidant in a transgenic mouse model of
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delays disease progression in ALS mice. Kieran D, Kalmar B, Dick JR,
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634325 Flavin-dependent antioxidant properties of a new series of meso-
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PHARMACOL 2004 67 1 77-85
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the metalloporphyrin class of superoxide dismutase mimetics. Tauskela
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J, Kalyanaraman B FREE RADIC BIOL MED 2002 33 7 988-997
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Marklund SL, Greenwood J, Lane RJ, deBelleroche J Clinical and functional
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80 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
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sensitive measure of superoxide radical. Gardner PR, Fridovich I J BIOL
CHEM 1992 267 13 8757-8763
638411 Long term administration of a small molecular weight catalytic
metalloporphyrin antioxidant AEOL 10150 protects lungs from radiationinduced
injury. Aeolus Pharmaceuticals Inc COMPANY PRESENTATION
2005 October 16-20

Vivitrex Alkermes/Cephalon
Christine E Heading
Address
Faculty of Science
The Open University in the North
Eldon House
Regent Centre
Gosforth
Newcastle-upon-Tyne
NE3 3PW
UK
Email: moore11@globalnet.co.uk
Current Opinion in Investigational Drugs 2006 7(1):81-88
© The Thomson Corporation ISSN 1472-4472
Vivitrex, an injectable, sustained-release formulation of the
opioid antagonist naltrexone, is being developed by Alkermes
and Cephalon for the potential once-monthly treatment of
alcoholism and opiate use disorder. Alkermes and Cephalon are
currently awaiting Food and Drug Administration review of
the Vivitrex new drug application, which was granted Priority
Review in May 2005.
Introduction
Vivitrex is an injectable, extended-release naltrexone
product that is currently in development by Alkermes Inc
and licensee Cephalon Inc for alcohol and opiate
dependence. Pharmacotherapies for substance-dependent
conditions have traditionally focused on the substance itself;
substitutes for the substance of abuse, plus receptor
antagonists and agents that interfere with the
pharmacokinetics of the substance (eg, methadone and
naltrexone for opiate dependence and disulfiram for alcohol
dependence) have all proved useful in treating these
conditions, and continue to be developed. However, there is
reliable evidence to suggest that certain loci in the brain
function abnormally in all dependencies, regardless of their
cause [636843]. Within the mesolimbic dopamine system
(MLDS) is the nucleus accumbens (NA), which is associated
with reward and drug-seeking behavior caused by the
elevation of dopamine levels at the site. Both alcohol and
opiates can raise levels of dopamine in the NA, and the
available evidence suggests that alcohol causes this by
increasing the release of endogenous opioids [631895].
Therefore, inhibition of opioid receptors by naltrexone is a
rational way of reducing the rewards that both ethanol and
opiates induce.
In 1984, the opioid receptor antagonist naltrexone was
approved for the treatment of opiate dependence in the US;
a decade later naltrexone was approved for the treatment of
alcohol dependence [631898]. The drug has also been
investigated for a variety of other dependencies. Naltrexone
acts at µ-, δ- and κ-opioid receptors, each of which are
implicated in one or more aspects of alcohol and opiate
dependence. Of the three receptors, the µ-opioid receptor is
believed to be the most significant regarding alcohol and
opioid self administration, and its absence or blockade tends
to be linked with diminished dependence [638453]. The
general evidence supporting the use of naltrexone for
alcohol dependence, as well as the relationship between
Originator Alkermes Inc
Licensee Cephalon Inc
Status Pre-registration
.
Indications Alcoholism, Opiate dependence.
.
Action Opioid antagonist
.
Technologies Controlled release formulation, Intramuscular
formulation
Synonym naltrexone (once-monthly controlled-release,
Medisorb)
Registry No: 16590-41-3
N
OH
HO O H O
81
opioid receptors and alcoholism, can be found in a
comprehensive review by Oswald and Wand [631895], and a
broad overview of the actions of naltrexone and its use in
the treatment of opiate dependence can be found in a review
by Kreek et al [638453].
Several factors make the worldwide extent of abuse of
and/or dependence on alcohol or opiates hard to quantify
accurately. The distinction between heavy use and
dependence is regularly blurred and the quoted figures are
often outdated, but it has been claimed that around 10 to 14
million individuals in the US are alcohol dependent
[631992], [637673]. Several gender-linked differences are
associated with alcohol use and dependence. One example
of such a difference is in incidence: an estimated 14% of men
and 5% of women in the US will experience symptoms of
alcohol abuse or dependence during their lifetime [637682].
Naltrexone is one of several therapeutic options for treating
opiate or alcohol dependence. Despite its oral
administration, a major limitation with this treatment is poor
patient compliance [593795]. One of several contributors to
this poor compliance may be the high plasma levels of the
metabolite 6β-naltrexol that result from first-pass
metabolism [638460]. The presence of this metabolite has
been correlated with both treatment dropout [638459] and
an increasing incidence of side effects [631898]. In a study by
King et al, individuals who experienced more side effects
had significantly higher urinary levels of 6β-naltrexol
following oral naltrexone treatment [638460]. In contrast,
there is some evidence that the metabolite could be valuable
in the treatment of opiate addicts; a reduction of the
withdrawal effects associated with µ-opioid receptor

82 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
antagonism by 6β-naltrexol may offer an advantage in
treating opioid overdose and addiction [638466]. More
certain contributors to poor patient compliance with oral
naltrexone include fluctuating levels of naltrexone in the
body and a lack of sustained motivation for overcoming the
addiction [616446], [636722].
Because of the problems with side effects and patient
compliance, several long-acting naltrexone preparations
have been explored by various research laboratories and
clinics since the early 1970s [441894], [616446], [637696],
[637699], but many remained experimental and lack product
licenses [636732]. Reported reasons for the failure to
commercialize these products include a paucity of evidence
of clear success, naltrexone-release problems and injectionsite
reactions [616446], but a lack of interest in developing
these products also seems to have played a role [636732].
Despite these hurdles, the development of Vivitrex, a depotrelease
naltrexone product, is almost complete, and the
product is nearing approval in the US [624146]. Similar
products in development include a sustained-release,
injectable depot formulation of naltrexone from DrugAbuse
Sciences Inc, which had reached phase III clinical trials for
opiate dependence by 2002 [455296], and an implant for
opiate dependence (naltrexone-poly(DL-lactide)) which has
been used experimentally for several years in Australia. By
2003, the DrugAbuse Sciences product had successfully
completed one phase III clinical trial for alcoholism [475512],
[638704] and the Food and Drug Administration has agreed
on the protocol for a second, pivotal phase III clinical trial in
alcohol-dependent patients. If this trial is successful,
DrugAbuse Sciences expects that the product could be
approved in the US and in Europe in 2008 [638704]. The
naltrexone implant product is in development by Go
Medical Industries Pty Ltd and is currently undergoing
clinical trials [631995].
To date, Vivitrex has only reached phase II clinical trials for
opiate dependence and, because of a lack of results for this
indication, this review will concentrate primarily on alcohol
dependence. Successful phase III clinical trial results have
lead Alkermes to predict a 2006 launch of Vivitrex for
alcohol dependence [632485], and the FDA was scheduled to
rule on US approval for this indication by the end of 2005
[624146].
Synthesis and SAR
Vivitrex is an extended-release depot injection of naltrexone
in which the active ingredient is encapsulated into
biodegradable polymer microspheres. These are fabricated
from poly-lactide co-glycolide (PLG), a common medical
polymer used in absorbance and extended-release
pharmaceuticals, to form microspheres approximately 100
µm in diameter [616446]. Alkermes's proprietary Medisorb
technology is used to produce microspheres that, following
subcutaneous or intramuscular administration, can maintain
a steady release rate of naltrexone into the bloodstream for
up to 1 month [593795], [616446].
Following injection into the body, PLG hydrolyzes to lactic
and glycolic acids. These naturally occurring metabolic
intermediates are further metabolized into carbon dioxide
and water. The ratio of lactide to glycolide in the polymer,
the molecular weight of the polymer, and other
manufacturing conditions all influence the rate of release of
the drug from the microsphere [616443].
Preclinical development
Studies conducted in animals confirmed that a single dose of
Vivitrex can antagonize the effects of morphine over a
period of at least 4 weeks [616446]. In the rat hot plate test,
the effect of placebo or Vivitrex on morphine-induced
analgesia was assessed over a period of up to 70 days.
Baseline testing was conducted prior to rats being assigned
to a treatment group. Every 5 days, analgesia was induced
with an intraperitoneal injection of morphine (1 mg/kg) and
the latency of hot plate response was detected 30 min later.
Rats pre-dosed with Vivitrex (50 mg/kg) administered
subcutaneously or intramuscularly showed a reduced
latency from day 1 to day 28 following injection (40 ± 0.54 s
and 36 ± 0.40 s following subcutaneous and intramuscular
injection, respectively) compared with placebo-treated rats
(57 ± 0.60 s), suggesting a substantial block of morphine
analgesia. Studies involving a second intramuscular
injection of Vivitrex (50 mg/kg), administered on day 34,
were conducted in the same model; an intramuscular
injection was used because it was thought to be the best
route for Vivitrex administration to humans. This injection
produced a similar effect to the initial treatment and
suppressed morphine-induced analgesia up to day 68 of the
study [616446].
Vivitrex-induced changes in µ-opioid receptor density and
immunoreactivity were assessed in rats from the same
experimental groups. As mentioned previously, the µ-opioid
receptor appears to be the opioid receptor that is most
strongly linked to alcohol and opiate dependencies [638453].
Rats were sacrificed over a range of days (from day 3 to day
40) and µ-opioid receptor density was examined in saturation
binding assays using [ 3H]DAMGO (D-ala 2, N-methyl-phe 4,
glycol 5-enkephalin) and using autoradiography and
immunoreactivity [616446]. Receptor density increased up to
2-fold following a single intramuscular injection of Vivitrex
(50 mg/kg). Receptor density in the midbrain and striatum
increased within 7 days by 100 and 110%, respectively,
compared with placebo treatment, whereas density in the
cortex increased by 120% between days 32 and 40 [616446].
No specific reason is known for these regional differences,
but the distribution, binding and elimination characteristics
of naltrexone in brain tissue may be relevant in determining
which regions of this organ are most closely linked to
dependency [616446].
Similar results were obtained using radioligand binding
autoradiography in rats receiving one or two intramuscular
injections of Vivitrex (50 mg/kg) 34 days apart, monitored 1
or 2 months after the initial injection [616446]. Radioligand
binding was significantly increased in all brain regions
studied, ranging from 90% in the habenular nucleus to 160%
in the dorsal raphe nucleus after 1 month. In the majority of
regions, density increased further in the following month,
reaching 120% in the habenular nucleus and 220% in the

dorsal raphe nucleus. Immunohistochemistry at adjacent
brain sections revealed increased µ-opioid receptor
immunoreactivity at both 1 and 2 months after Vivitrex
injection; however, the effect was less than in the
autoradiography studies, with only two of the 15 brain
regions examined showing significant increases over control
after 1 month. The investigators of the report interpreted the
large increase in µ-opioid receptor density, but small
increase in µ-opioid receptor immunoreactivity, as evidence
of recruitment of active µ-opioid receptors from a pool of
receptors, rather than an increase in µ-opioid receptor
protein expression [616446].
Metabolism and pharmacokinetics
A single intramuscular or subcutaneous injection of Vivitrex (50
mg/kg) produced stable, pharmacologically relevant plasma
concentrations in rats for approximately 1 month. AUC values
of 332 and 360 ng.day/ml were observed following
intramuscular and subcutaneous administration, respectively.
Maximum naltrexone plasma levels (15 ± 1.4 and 19 ± 3.6
ng/ml following subcutaneous and intramuscular
administration of Vivitrex, respectively) were produced within
3 days, with half-maximum levels reached within 24 h. By 35
days, naltrexone plasma concentrations were approaching
undetectable levels (< 1 ng/ml), and a similar pattern was
observed following a second Vivitrex injection [616446].
Naltrexone is primarily metabolized by the liver, producing the
major metabolite 6β-naltrexol. This metabolite can be detected
in both conjugated and non-conjugated form in plasma.
Following oral administration, 1% of unchanged naltrexone is
excreted in urine [631898]. The half-life of oral naltrexone in
humans is 4 to 9 h, compared with 12 to 18 h for 6β-naltrexol
[631895], but using the Vivitrex formulation, the half-lives of
naltrexone and 6β-naltrexol are greatly extended, and are
quoted as 5 to 8 days [636722]. The pharmacokinetic benefits of
the extended-release injection compared with oral dosing
include an absence of high peak plasma concentrations, a
decrease in gastrointestinal exposure, and avoidance of firstpass
hepatic metabolism [616446]. Compared with oral
naltrexone, Vivitrex reduces the ratio of 6β-naltrexol to the
parent compound in the body [593795], [616443], which is
consistent with findings of studies with other extended-release
preparations. This reduction is thought to result from
avoidance of the first-pass effect [631898].
In a phase I, double-blind clinical trial, 42 healthy volunteers
were randomized to receive placebo or Vivitrex as a single
intramuscular (150, 300, 600 or 900 mg) or subcutaneous
(150, 300 or 600 mg) injection [390669]. Preliminary data
regarding plasma levels of naltrexone showed that the AUC
and Cmax values were dose proportional, with slightly higher
values observed following intramuscular dosing (at 150, 300
and 600 mg; intramuscular AUC values of 49 ± 9, 84 ± 12 and
189 ± 27 ng.day/ml were observed compared with
subcutaneous AUC values of 31 ± 11, 65 ± 13 and 145 ± 28
ng.day/ml, respectively). The initial drug 'burst' (within 48
h) demonstrated a peak concentration that was only
approximately 3-fold higher than steady-state levels, which
were dose proportional, within expected therapeutic levels,
and maintained for a full month [390669].
Vivitrex Heading 83
Results from a phase II clinical trial in 30 alcohol-dependent
patients administered intramuscular Vivitrex (400 mg)
showed that mean trough serum naltrexone concentrations
remained relatively constant throughout the study (1.23
ng/ml). Mean serum trough levels of 6β-naltrexol (2.91
ng/ml) were slightly higher than naltrexone, but
substantially lower than those observed following oral
naltrexone administration. As outlined above, lower levels
of 6β-naltrexol are thought to reduce the chances of adverse
events and improve patient compliance [616443].
Because individuals who consume large quantities of
alcohol often suffer from liver damage, the
pharmacokinetics of Vivitrex were examined in patients
with mild-to-moderate hepatic impairment [636722]. Six
individuals with mild (Child-Pugh grade A) or moderate
(Child-Pugh grade B) hepatic impairment and 13 healthy
individuals each received a single intramuscular dose of
Vivitrex (190 mg). The total exposure (AUC0-∞) of naltrexone
and 6β-naltrexol was similar across all groups over 63 days
(treatment comparison ratios were 0.97 and 1.08 for mild
and moderate hepatic impairment, respectively, compared
with control), indicating that no dosage adjustment would
be needed for alcohol users with impaired liver function
[636722].
Toxicity
No toxic effects have been reported in animal studies,
although the increased density of µ-opioid receptors
observed in rats poses a theoretical risk in the context of
opiate abuse. Similar, long-lasting receptor changes have
been observed with other naltrexone formulations and can
potentially enhance hypersensitivity to opiates. The effects
have also been observed with other opiate antagonists, and
it has been suggested that the change results from the
recruitment of receptors from a pool of receptors in response
to the presence of antagonists [616446]. From indirect
evidence, it has been suggested that the enhanced
hypersensitivity induced by Vivitrex is unlikely to increase
the euphoria, respiratory depression and tolerance that can
result from the intake of opiates [616446]. In contrast, there
is long-standing experimental evidence that hypersensitivity
to the analgesic effects of opiates can occur after naltrexone
exposure [638481], [638482].
Clinical development
Phase I
In the phase I, randomized, double-blind, placebo-controlled
study in which 42 healthy volunteers received either placebo
or single doses of Vivitrex in an escalating-dose paradigm
(intramuscular injections of 150, 300, 600 or 900 mg, or
subcutaneous injections of 150, 300 or 600 mg), therapeutic
levels of naltrexone were sustained for 1 month. In order for
equivalent plasma levels to be achieved over this period
using oral naltrexone, the total naltrexone dose would need
to be 5-fold higher [393208].
Phase II
A multicenter, randomized, double-blind, placebocontrolled
pilot study was conducted with 30 patients with a
DSM-IV diagnosis of alcohol-dependence. Vivitrex (400 mg)

84 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
was administered intramuscularly once a month for 4 months
to 25 patients, and the remaining patients were given placebo;
both groups were offered psychosocial support [494451],
[616443]. At the end of this period, the mean percentage of
heavy drinking days in the Vivitrex group was reduced to half
that of the placebo group (11.7% compared with 25.3%).
Patients treated with Vivitrex also showed an increase in the
mean percentage of days abstinent from alcohol (69.4%
compared with 39.2% pre-treatment) and a reduction in the
number of drinks consumed per drinking day (3.8 compared
with 7.4 pre-treatment) [616443].
A trial designed to determine the pharmacokinetics and
safety of a range of Vivitrex doses in opiate-dependent
individuals was initiated in 2002 [445176], but by November
2005, no results were apparently available.
Phase III
A 6-month, double-blind, placebo-controlled, randomized
study was conducted at 24 centers in 624 patients (423 men
and 201 women) with DSM-IV-diagnosed alcohol
dependence [593795]. All study groups were matched for
men and women and patients received monthly
intramuscular injections of Vivitrex (190 or 380 mg; n = 210
and 205, respectively) or placebo (n = 209). All groups also
received low-intensity counseling. Patients receiving 380 mg
Vivitrex showed a 25% reduction in heavy drinking (defined
as five or more drinks per day for men and four drinks per
day for women) compared with the placebo group (p =
0.02). In patients receiving 190 mg Vivitrex, heavy drinking
was reduced by 17% compared with patients receiving
placebo (p = 0.07). Overall, the median number of heavy
drinking days in the group receiving 380 mg Vivitrex was
reduced from 19 to 3 days a month [593795].
Considering each gender separately, the number of heavy
drinking days for males receiving the high dose of Vivitrex fell
by 48% compared with males given placebo (p < 0.0001),
whereas the results from females treated with Vivitrex did not
differ from those given placebo. Similarly, males administered
low-dose Vivitrex showed a 25% reduction in heavy drinking
days compared with placebo (p < 0.03), but there was no
difference between the results from females treated with either
Vivitrex or placebo [516479], [593795].
Results of an open-label, 12-month extension trial that enrolled
85% of individuals who completed the initial phase III trial
were presented in May 2005 [603348]. The results confirmed the
sustained efficacy of Vivitrex. The trial recruited 115 of the 380mg
dose patients, 102 of the 190-mg group and 60 patients from
the placebo group. Gender was not a recruitment criterion.
Patients from the placebo group were randomized to receive
either 380 or 190 mg Vivitrex by monthly intramuscular
injection. Patients in the high-dose group showed a reduction
(not claimed as significant) in the median number of heavy
drinking days per month from 2.6 to 1.6 days. Patients switched
from placebo to 380 mg Vivitrex showed a reduction in heavy
drinking days from 5.2 to 1.8 days per month [603348].
There was evidence of a physiological improvement
secondary to the reduction of alcohol intake from both the
phase II and III trials, as indicated by a reduction in the level
of the hepatic enzyme γ-glutamyl transferase (GGT; a liver
enzyme raised in ~ 70% of alcohol abusers that is frequently
used as a marker of reduced alcohol intake) [638730]. A
mean reduction in serum activity of GGT was observed in
both the phase II clinical trial [616443] and in the phase III
clinical trial [593795].
Side effects and contraindications
As discussed, Vivitrex is designed to reduce a number of
problems associated with other naltrexone formulations,
including the high concentration of its primary metabolite,
which may contribute significantly to the side effects
observed with oral naltrexone. In studies with other
naltrexone formulations, 6β-naltrexol was linked with
subjective reports of headache, nausea and anxiety [631898].
Preliminary analysis of the results from clinical trials
indicated that Vivitrex was well tolerated and demonstrated
no serious adverse events in healthy volunteers [390669],
findings that were subsequently confirmed in patient trials.
However, the side effects of substance dependence
treatments often depend on the substance being abused.
Substance abusers often fail to adhere to the planned
therapeutic program so that the treatment drug may at some
point be used alongside the abused substance. Thus, the
risks associated with the use of Vivitrex for alcohol
dependence differ from those that arise when the product is
used for opiate dependence. It is also noteworthy that
abusers might increase their level of usage in order to
surmount a blockade of effect produced by Vivitrex.
In a phase II trial of 30 patients with alcohol dependence, an
intramuscular injection of Vivitrex (400 mg) was generally safe
and well tolerated, and reported adverse effects were mild to
moderate. Nausea and headache were the most common
adverse events, and both occurred equally in the placebo- and
Vivitrex-treated groups [432929]. However, two patients
discontinued participation in the study because of adverse
events (injection site induration and angioedema). Both events
occurred after the second, monthly dose of Vivitrex and were
moderate in severity [616443].
In the 6-month, 624-patient phase III trial involving alcoholdependent,
active drinkers, trial discontinuation owing to
adverse events occurred in 14.1% of the 380-mg naltrexone
group, 6.7% of the 190-mg group, and 6.7% of the placebo
group [593795]. At least 10% of patients experienced some
form of adverse event following Vivitrex treatment, but less
than 2% of patients discontinued treatment because of
injection-site reaction [534413]. The most common adverse
effects in the main trial were nausea, headache and fatigue,
all of which have been observed with oral naltrexone
formulations [593795]. Nausea was mild or moderate in 95%
of cases, and usually occurred during the first month. As
well as loss of appetite, this was the most common adverse
event in the 380-mg dose group. The frequency of serious
adverse effects during the trial was similar in all treatment
groups, the most common being hospitalization for alcohol
intoxication. However, two cases of pneumonia occurred in
the 380-mg group and, although not observed with
naltrexone or microsphere medications previously, may

have been related to Vivitrex. Mean levels of alanine
aminotransferase and aspartate aminotransferase did not
change significantly, indicating a lack of hepatotoxicity
[593795]. The most common adverse effects in the 12-month
extension trial were headache, nasopharyngitis and
respiratory tract infections [603348].
Patent summary
Naltrexone was originally claimed by Endo Laboratories Inc
in 1967 (US-03332950). This patent expired in 1984, and by
the late 1980s, any basic product protection elsewhere had
also expired. The Medisorb extended-release technology was
first claimed in WO-09742940 and granted as US-05817343
and EP-00914095 in July 2002. Originally developed by
Medisorb Technologies International LP, the method was
acquired by Alkermes in 1996.
The patent status for Vivitrex will be resolved when it has been
granted FDA approval (which was expected in December 2005)
and a selection of relevant patents is subsequently published in
the Orange Book. Alkermes has claims to various patents
covering areas such as the injectable, extended-release of
naltrexone compositions (WO-2004103342) and amorphous and
polymorphic forms of naltrexone, which are reported to be
advantageous in extended-release formulations (WO-
2004108084). Moreover, two further patent applications (WO-
2005089449 and WO-2005089486) cover combinations of
naltrexone with an anticonvulsant or a dopamine D2 partial
agonist for treating alcoholism.
Current opinion
A full understanding of how opioids influence reward
pathways is not yet available, but occupancy of opioid
receptors by endogenous peptides or opiate drugs is known
to influence the MLDS [631895]. Most experts in the field of
neuroscience consider that this pathway plays a major role
in reward mechanisms and drug-seeking behavior, and
believe that the sensitization of the MLDS observed in
dependence reflects a form of learnt or conditioned
behavior. The various behavioral hypotheses that attempt to
explain dependence generally share the view that the effect
experienced after substance intake reinforces the substanceseeking
behavior [636843]. If the link between intake and
effect is broken (eg, by pharmacotherapeutic means) the
learnt behavior can be overcome [631895], [636843].
Pharmacotherapy alone rarely succeeds in eliminating
dependence, but where patients have the correct motivation
and psychosocial support, reductions in dependence can be
achieved. It is therefore reasonable for clinical trials to
incorporate both pharmacological and psychological
elements. However, when interpreting the results of the
phase II and phase III clinical trials of Vivitrex to date, it
should be noted that they are placebo-controlled trials and
do not compare psychosocial therapy alone with
psychosocial therapy plus Vivitrex. It is perfectly possible
that psychological elements of a placebo effect contributed
to the improvements in the placebo-treated groups, and the
design of the studies has wisely avoided the need to
establish whether this is the case. It is also possible that
genders respond differently to the psychological elements of
treatment and much here remains to be elucidated.
Vivitrex Heading 85
As discussed previously, the value of oral naltrexone in the
long-term treatment of alcohol or opiate dependence has been
greatly undermined by the failure of the substance abusers to
adhere to the daily dosing schedule [593795]. A reliable
extended-release preparation that uses the intramuscular route
should provide an answer to the fluctuating plasma levels of
naltrexone and high plasma levels of the naltrexone metabolite,
and circumvent the changeable motivation seen in the users.
Vivitrex is therefore likely to be welcomed as a new treatment
for alcohol dependence that can be initiated in active drinkers,
especially when considering the current absence of any truly
satisfactory alternative products. Disulfiram and acamprosate
are options for therapeutic intervention in alcohol abuse, but
both have limitations and, in contrast to Vivitrex, are not
considered suitable for initiation in active alcohol users
[631992], [638487]. Disulfiram relies on an aversive effect
produced by altered metabolism of ethyl alcohol, but the
adverse side effects associated with this drug can be severe and
even fatal [631992], [638487]. Acamprosate is thought to act on
γ-aminobutyric acid and glutaminergic receptors, with at least
some of its actions being focused on the NA [631992].
To date, the efficacy of Vivitrex has been confirmed for
alcohol dependence only and, specifically, only in men. The
trial report suggests that the difference in efficacy may be a
consequence of different patient characteristics (eg, weight,
smoking and use of antidepressants) rather than a
fundamental gender difference, but establishing widespread
efficacy in women may be difficult. Clinicians may also be
reluctant to use depot preparations in women who might
become pregnant because of the universal principal of
minimizing medication during the first trimester. A nonchemical
treatment or one that can be halted abruptly might
be preferred for women of childbearing age.
Should Vivitrex be developed further for opiate dependence,
the safety issues will be different to those for alcohol
dependence. Naltrexone is currently prescribed only for
opiate addicts who are not active users because this agent
can precipitate opiate withdrawal effects in active opiate
users [631992]. Thus, to combat opiate abuse, Vivitrex might
be more suited to use in an in-patient, rather than
community, environment, where it would be harder for
users to increase their opiate intake in an attempt to
surmount the naltrexone-induced opioid antagonism.
Finally, it should be acknowledged that a great deal remains
to be understood regarding dependence on opiates and
alcohol as well as appropriate treatments. For example, µopioid
receptors have been researched and implicated in
dependence far more than δ- and κ-opioid receptors, which
may also be involved. At the receptor level, adaptive
responses to alcohol or opiates are known to occur, and
adaptive responses to antagonists are also observed. These
responses have been observed with Vivitrex treatment, and
the implications of such responses are not yet clear. In
addition, from the behavioral point of view, the possible
beneficial action of Vivitrex on craving has not yet been
explored. Overall, it seems probable that Vivitrex has the
capacity to make a significant contribution to the treatment
of dependence long before its detailed mode of action has
been elucidated.

86 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
Commercial opinion
In November 2005, an analyst from SunTrust Robinson
Humphrey stated that they believed that it would take some
time to build the market for Vivitrex for alcoholism, and that
peak sales could reach US $250 million in the future.
Predicted sales of Vivitrex in fiscal 2007 (beginning in
the second quarter of 2006) were estimated at
US $65 million, leading to sales of US $110 million in
fiscal 2008, rising to US $175 million in fiscal 2010
[638339].
Licensing
Cephalon Inc
In June 2005, Cephalon agreed to jointly develop and commercialize Vivitrex in the US. Alkermes was to receive an initial
payment of US $160 million from Cephalon and will receive an additional US $110 million if Vivitrex is approved, and could
also receive up to US $220 million in milestone payments based on sales. The responsibility for developing the commercial
strategy for the product will be shared by a joint commercialization team formed from both companies. Alkermes will be
responsible for manufacturing Vivitrex and seeking marketing approval and Cephalon will conduct the marketing and sales
of the product. Alkermes will be responsible for any cumulative losses of up to US $120 million until December 31 2007, or
for 18 months after FDA approval. During this period, Cephalon will be liable for cumulative losses exceeding US $120
million. After that time, any pretax profit or loss will be shared equally by both companies [609280].
Development history
Developer Country Status Indication Date Reference
Alkermes Inc US Pre-registration Alcoholism 01-APR-05 592847
Cephalon Inc US Pre-registration Alcoholism 24-JUN-05 609507
Alkermes Inc US Phase II Opiate dependence 22-JAN-02 435928
Literature classifications
Chemistry
Study type Result Reference
Preparation. Naltrexone is encapsulated into biodegradable polymer microspheres (100 µm diameter) fabricated
from PLG. Following subcutaneous or intramuscular administration, the microspheres can maintain a
steady release rate of naltrexone into the bloodstream for up to 1 month.
616446
Biology
Study type Effect studied Model Result Reference
In vivo Efficacy. The latency of response in a hot plate test Reduced latency from day 1 to 28 616446
was measured in rats 30 min after a was observed in rats pre-dosed with
1.0-mg/kg intraperitoneal morphine Vivitrex (40 ± 0.54 s and 36 ± 0.40 s
injection (administered every 5 days). following subcutaneous and
Rats were administered a single 50- intramuscular injection, respectively)
mg/kg dose of Vivitrex either
compared with placebo-treated rats
subcutaneously or intramuscularly prior to
testing.
(57 ± 0.60 s).
In vivo Efficacy. Post-sacrifice radioligand binding
autoradiography assays using
[ 3 Increased radioligand binding was 616446
observed in all brain regions
H]DAMGO were used to measure examined, reaching 120% in the
receptor density in rats for up to 2 months habenular nucleus and 220% in the
following a 50-mg/kg intramuscular
injection of Vivitrex.
dorsal raphe nucleus.
In vivo Efficacy. Post-sacrifice immunohistochemistry The increase in receptor
616446
using receptor-targeting antibodies in rats immunoreactivity was less than in
1 or 2 months following a 50-mg/kg the autoradiography studies, with
intramuscular injection of Vivitrex.
only two of the 15 brain regions
examined showing significant
increases after 1 month compared
with control.
Metabolism
Study type Effect studied Model Result Reference
In vivo Pharmacokinetics. Circulating levels of naltrexone in AUC = 332 and 360 ng.day/ml and Cmax = 616446
rats measured 1 to 35 days 15 ± 1.4 and 19 ± 3.6 ng/ml after
following subcutaneous or
subcutaneous and intramuscular
intramuscular administration of administration of Vivitrex, respectively. By
Vivitrex (50 mg/kg).
day 35, drug levels were almost
undetectable (< 1 ng/ml).

Metabolism (continued)
Vivitrex Heading 87
Study type Effect studied Model Result Reference
In vivo Pharmacokinetics. Phase I, double-blind study of 42 AUC and Cmax were dose proportional, with 390669
healthy volunteers randomized to slightly higher values observed following
receive placebo or Vivitrex as a intramuscular administration (AUC = 49 ±
single intramuscular (150, 300, 9, 84 ± 12 and 189 ± 27 ng.day/ml at 150,
600 or 900 mg) or subcutaneous 300 and 600 mg, respectively) compared
(150, 300 or 600 mg) injection. with subcutaneous administration (AUC =
31 ± 11, 65 ± 13 and 145 ± 28 ng.day/ml at
150, 300 and 600 mg, respectively).
In vivo Pharmacokinetics. Phase I, double-blind study of 42 Therapeutic naltrexone levels were
393208
healthy volunteers randomized to sustainable for a full month. Sufficient
receive placebo or Vivitrex as a doses were 5-fold less than the equivalent
single intramuscular (150, 300, dose required through oral naltrexone
600 or 900 mg) or subcutaneous
(150, 300 or 600 mg) injection.
administration.
In vivo Pharmacokinetics. Phase II, double-blind study of 30 The mean trough serum naltrexone
616443
healthy volunteers randomized to concentration remained relatively constant
receive intramuscular Vivitrex (400 throughout the study. Serum levels of 6β-
mg) or placebo once a month for 4 naltrexol were substantially lower than
months.
those observed following oral naltrexone
administration.
In vivo Pharmacokinetics. Control-matched study in
individuals with mild or moderate
Total exposure (AUC0-∞) of naltrexone and
6β-naltrexol was similar across all groups
636722
hepatic impairment. Six individuals over 63 days (treatment comparison ratios
from each test group and 13 were 0.97 and 1.08 for mild and moderate
healthy volunteers each received a hepatic impairment, respectively,
single 190-mg intramuscular dose compared with control) indicating that no
of Vivitrex.
dosage adjustment would be needed for
alcohol users with impaired liver function.
Clinical
Effect studied Model Result Reference
Efficacy. Phase II, multicenter, randomized, The mean percentage of heavy drinking days was
616443
double-blind pilot study conducted with 30 reduced to 11.7% in the Vivitrex group compared with
alcohol-dependent patients who received 25.3% in the placebo group. An increase in the mean
a 400-mg intramuscular injection of percentage of days abstinent from alcohol (69.4%
Vivitrex (n = 25) or placebo (n = 5) once a compared with 39.2% pre-treatment) and a reduction in
month for 4 months. Both treatment the number of drinks consumed per drinking day (3.8
groups received counseling.
compared with 7.4 pre-treatment) was seen with Vivitrex
treatment.
Safety and Phase II, multicenter, randomized, Vivitrex was well tolerated and adverse effects were 616443
tolerability. double-blind study conducted with 30 mild to moderate. Nausea and headache occurred
alcohol-dependent patients who received
intramuscular injections of 400 mg
Vivitrex (n = 25) or placebo (n = 5) once a
month for 4 months.
similarly in both patient groups.
Efficacy. Phase III, double-blind, placebo-
There was a 48% reduction in heavy drinking days for 516479
controlled, randomized clinical trial in 624 males administered the 380-mg dose compared with
alcohol-dependent patients. Patients were placebo (p < 0.0001), whereas in females the results did
enrolled to receive Vivitrex (190 or 380 not differ from placebo. Similarly, males administered
mg) or placebo once a month for 6 190 mg Vivitrex showed a 25% reduction in heavy
months. All patients received counseling. drinking days compared with placebo (p < 0.03), but
there was no difference in the results from females
treated with either Vivitrex or placebo.
Efficacy and A 12-month, open-label extension of a Patients who continued on the 380-mg dose showed a 603348
tolerability. phase III clinical trial in 277 patients sustained reduction in the median number of heavy
administered monthly intramuscular drinking days per month (2.6 to 1.6 days). Patients
injections of Vivitrex (380 or 190 mg). switched from placebo to the 380-mg drug dose showed
Patients formerly on placebo were a reduction in the median number of heavy drinking
switched randomly to either the 380- or days from 5.2 to 1.8 days per month. Vivitrex was well
190-mg Vivitrex groups.
tolerated over the total 18-month period.
Associated patent
Title Method for fabricating polymer-based controlled-release devices.
Assignee Alkermes Inc
Publication WO-09742940 20-NOV-97
Priority US-19960649128 14-MAY-96
Inventor Burke PA.
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88 Current Opinion in Investigational Drugs 2006 Vol 7 No 1
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Erratum
Current Opinion in Investigational Drugs (2005) 6(7):686-689.
Mario di Napoli & BethAnn McLaughlin
In the legend to Figure 1, PPi is an abbreviation of inorganic pyrophosphate.
89