Safety and efficacy assessment of plerixafor in patients with multiple myeloma proven or predicted to be poor mobilizers, including assessment of tumor cell mobilization.

This was an open-label, single-center, phase II study of 20 patients with multiple myeloma who were either proven poor mobilizers (n=10; group A) or predicted poor mobilizers (n=10; group B) and were planned for autologous hematopoietic SCT. The aim was to assess the safety and efficacy of plerixafor for stem cell mobilization and tumor cell contamination. The peripheral blood (PB) CD34+ cell count was generally very low pre- plerixafor and increased significantly post-plerixafor administration. Cumulative apheresis yields of > or =2 x 10(6) CD34+ cells/kg were observed in 7 of 10 patients (group A) and 8 of 10 patients (group B). Among the proven poor mobilizers, there was no evidence of tumor cell mobilization in the PB after G-CSF plus plerixafor treatment. Seventeen of 20 (85%) patients underwent transplantation. Neutrophil engraftment occurred at a median of 13 days for all patients. Platelet engraftment occurred at a median of 16 days and 19 days for all proven and predicted poor mobilizers, respectively. At 12 months, 12 of 17 patients had documented durable grafts, 3 of 17 patients died and 2 of 17 patients were lost to follow-up; but they had documented graft durability at the previous 3- and 6-month visit. The safety profile of plerixafor in all patients was consistent with previous reports.