Stem Cell Mobilization Using 5 Pm Dosing of Plerixafor.

Based on the superiority of plerixafor plus G-CSF (PG) compared to G-CSF (G) alone for mobilizing autologous stem cells, PG has been approved for stem cell mobilization in patients with multiple myeloma and NHL. PG may also be useful for mobilizing stem cells in patients who have failed mobilization with G alone or chemotherapy plus G. Although pivotal studies in myeloma and NHL employed evening (10 pm) dosing of P in order to capture peak mobilizing activity of PG 10-11 hours later, this schedule is inconvenient. Methods: A regimen using 5 pm dosing of P was employed in 17 patients (9 NHL, 7 myeloma, 1 germ cell tumor) including 10 patients who received PG and 7 pts who transitioned to PG after chemo plus G. Apheresis was performed at 8:30 am after P. Four patients had failed previous mobilization with chemo plus G and 4 pts were expected to be poor mobilizers because of prior Rx (lenalidomide 3, fludarabine 1). In nine patients, P was added to G (2 pts) or chemo plus G (7 pts) during the mobilization episode because of inadequate stem cell collections.

An engraftable dose (> 2.5 × 10E6CD34/kg) of stem cells was achieved in all eight pts who either failed prior mobilization or were anticipated to be poor mobilizers because of past Rx and in 6 of 9 pts who had P added during suboptimal mobilization with either G (2/2) or chemo plus G (4/7). In successfully mobilized pts (14/17), the median number of CD34 cells collected was 6 × 10E6/kg in two aphereses. In the latter group, the median CD34 count/μl on the first day after P was 29 (R: 11-161) and had increased a median of 4.5 fold (R: 2.75 – 40.2) compared to one day earlier. Six pts have had transplant with a median WBC and platelet recovery of 10 and 11 days, respectively. Conclusions: PG with 5 pm dosing of P and apheresis at 8:30 the next morning was effective in pts who failed prior mobilization and in pts expected to be poor mobilizers because of prior Rx. Further studies are required to determine the efficacy and optimal scheduling of P when added during suboptimal chemo plus G mobilization.

Off Label Use: Plerixafor is a stem cell mobilizing agent that is approved for multiple myeloma and NHL. One patient with a germ cell tumor has been included in this study of an alternative mobilization strategy. Foss:Eisai : Speakers Bureau.