Autologous Bone Marrow Transplantation - Blog Science Connections

Chemopurging 147
To date, four patients (one ALL and one mixed lineage in CR2, and two
AML—one in first CR [CR1] and one in CR2) have had ex vivo marrow
treatment. The final CFCI-GM recovery was between 0.46 and 1.87 x 10 4 /kg
body weight in these patients (see Table 3). The CFCI-GM recovery after ex
vivo chemotherapy ranged from 5% to 25%, corresponding to an IC74.95.
Table 4 shows the sequential CFCI-GM losses in our first clinical caserecovery
was as anticipated from previous in vitro experiments. The three
CR2 patients received CBV (cyclophosphamide, BCNCI [carmustine], VP-16-
213) preparation chemotherapy as described previously (13), followed by
their purged marrow. Hematologic recovery was a neutrophil count of
100/mm 3
by posttransplantation days 13,16, and 19; a neutrophil count of
500/mm 3 by days 15,23, and 36; platelet count of 50,000/mm 3 was achieved
by days 26, 31, and 36. The acceptable hematopoietic recovery in the
transplanted patients suggests that the multipotent hematopoietic stem cell
has not been seriously damaged, even after freezing.
Figures 1 and 2 show our overall ex vivo strategy for acute leukemic
patients in CR2. To overcome chemotherapy-resistant cells, we plan to add
magnetic separation, using monoclonal antibody (MAb) pools directed at
specific leukemia types. The antibodies are bound to a cobalt magnetic
affinity colloid (see Reading et at "Magnetic Affinity Colloid Elimination of
Specific Cell Populations From Bone Marrow," in this volume). Figure 1
shows the anticipated cell and CFG-GM losses when MAbs are combined with
chemopurging. Figure 2 outlines the planned stepwise development of a safe
and effective combined ex vivo regimen. Once we are confident that there is
still no compromise of hematopoietic recovery on subsequent patients
treated with ex vivo chemotherapy alone, the addition of immunomagnetic
separation will be investigated.
Minimal progenitor cell losses are anticipated with MAbs directed against
ALL cells. However, some antibodies reactive with myeloid leukemia cells
would be expected to reduce CFCI-GM numbers significantly. Both pools of
MAbs would result in mechanical losses of up to 50% CFCI-GM. Therefore, we
Table 3. Clinical Ex Vivo Purging'
CFU-GM/kg * 10
Patient
Aspirate
40-60% Percoll
Interphase Postpurging % IC
% Total
Recovery
1 28.96 9.47 1.87 80.3 6.5
2 37.69 12.44 0.56 95.5 1.5
3 5.05 2.33 0.62 73.6 12.2
4a 9.26 4.38 0.46 87.5 5.0
4b 1.21 1.03 0.08 92.2 6.6
"Using vincristine (1 uglml) + 4-hydroperoxycyclophosphamide (5 ug/ml).
Abbreviations: CFU-GM, granulocyte-macrophage colony-forming unit; IC,
inhibitory concentration.