Novel Functionalyzed 5-Aryl-2-furfuril-N-acylhydrazone Derivatives ...

CONFIDENTIAL
INCT-INOFAR Project: Novel Functionalyzed 5-Aryl-2-furfuril-N-acylhydrazone Derivatives
with Potent Antiinflammatory and Analgesic Activities: LASSBio-1609 e LASSBio-1636
Coordinator: Carlos A. Manssour Fraga, LASSBio, Institute of Biomedical Sciences, UFRJ
The diversity of mechanisms involved in the genesis of neuropathic pain makes especially
difficult the treatment of this disease, as well as the variable response of patients the same therapy,
the many adverse effects and interactions with other drugs. A very important point is that only
about a half of patients are able to obtain sufficient pain relief with currently available drugs
(Rogers et al., 2006).
For this reason, the main objective of this project is to synthesize and evaluate
pharmacologically novel furfuryl-N-acylhydrazone derivatives, designed by applying the azavinylogation
strategy on furfuramide derivatives described by Kort and co-workers (2008) as
blockers of the Nav 1.8 sodium channels, highlighting the compound A-803467, a selective blocker
of these channels (Figure 1).
A 3D-QSAR (CoMFA) model for the Nav 1.8 sodium channel was created to assist the
structural planning of the new family of furfuryl-N-acylhydrazone derivatives. This model is the
only 3D-QSAR model for a subtype of sodium channel described to date (Figure 1).
Cl
O
A-803467
O
N
H
OCH 3
OCH 3
Ar 1
O
O
N
H
Aza-vinylogy
N
R
Figure 1: Design concept of novel furfuryl-NAH derivatives.
Ar 2
The synthetic methodology employed for obtaining of the novel N-acylhydrazone
compounds consisted in four steps, all of them presenting high yields, involving reactions such as
Suzuki coupling, Yamada oxidation, hydrazinolysis and condensation (Scheme 1). In some steps,
procedure optimizations were made, through microwave reactions, in order to improve reaction
time and yield. All compounds of the new family of furfuryl-N-acylhydrazone derivatives were
obtained as a single diastereomer and 1D NOESY experiments carried out suggest that the relative
configuration presented by these derivatives is the E configuration. Elemental analysis, infrared and
mass spectra were also made, complementing the structural characterization of the new NAH
derivatives.
Scheme 1: Reagents and conditions: a) K 2 CO 3 , PdCl 2 [P(Ph) 3 ] 2 , i-PrOH/H 2 O, 80°C, MW; b) KOH,
I 2 , MeOH, 0°C; c) NH 2 NH 2 .H 2 O, EtOH, rt; d) ArCHO, EtOH, HCl cat , rt or ArCO(CH 3 ), MW, 80°C.

CONFIDENTIAL
Among these new N-acylhydrazone derivatives the compounds LASSBio-1609 and
LASSBio-1636, can be identified as authentic analgesic prototypes, as both showed improved
antinociceptive activity profile in animal models of inflammatory and neuropathic pain. These
derivatives were capable of decreasing the hipernociception induced by carrageenan and CFA in
mice at 30 and 100 µM concentration, showing a profile very similar to those showed by prototype
A-803467. Also, oral administration of compounds LASSBio-1609 and LASSBio-1636 produced
anti-allodynic and anti-hyperalgesic effects in rats in the Chung model (L5/L6 Spinal Nerve
Ligation - SNL) of neuropathic pain. These effects were comparable to those of the prototype A-
803467 in the same model (Figure 2). In addition, these derivatives proved to have high stability in
rat plasma, featuring, at least partially, an adequate bioavailability profile.
Figure 2: Antinociceptive effect of LASSBio-1609, LASSBio-1636 and A-803467 in SNL
neurophatic pain model in rats. (A) Thermic hypersensibility; (B) Mechanical allodynia.
The novel NAH derivatives LASSBio-1609 and LASSBio1636 did not affected the motor
coordination of mice as observed in the rota-rod test. Additionally, it is important to highlight that
the compounds only interfered with the threshold of nociception in the mice where inflammation
was induced, bringing it back to normal. However, in control mice, the compounds did not affected
the normal threshold for activation of pain. These results demonstrate that these prototypes act only
in the disease level, not affecting the normal physiological functions.
In an attempt to identify the specific molecular mechanism of action of LASSBio-1609 and
LASSBio-1636, electrophysiological (whole-cell patch-clamp technique) in vitro assay was
employed. As a source of NaV1.8 currents (the primary target of NAH derivatives) dorsal root
ganglion cultured neurons were used. To ensure that the NAH compounds are probably acting on
Nav1.8 TTX-R currents, TTX (100 nM) were added to the perfusion solution. It was observed that
even in the presence of TTX, there is a remaining current that is probably composed of Nav1.8 plus
Nav 1.9. The perfusion of cell with LASSBio-1636 (10 µM) reduced TTX-resistant currents. It is
noteworthy that the effect of LASSBio-1636 was washed out suggesting a surmountable effect. This
preliminary result is in line with the hypothesis that LASSBio-1636 is probably a Nav1.8 selective
blocker.
References:
- Kim, Sh; Chung, Jm (1992) An experimental model for peripheral neuropathy produced by
segmental spinal nerve ligation in the rat. Pain 50: 355-363.
- Kort, M. E. et al. (2008) Discovery and biological evaluation of 5-aryl-2-furfuramides, potent
and selective blockers of the Nav1.8 sodium channel with efficacy in models of neuropathic and
inflammatory pain. J. Med. Chem. 51: 407-416.
- Rogers M. et al. (2006) The role of sodium channels in neuropathic pain. Semin. Cell. Dev. Biol.
17:571-581.