Comparison of Graft Durability Among Lymphoma Patients Who Received Plerixafor in Combination with G-CSF for Primary Versus Failed Mobilization

Introduction: The addition of plerixafor to G-CSF (P + G) successfully mobilizes sufficient hemtopoietic stem cells (HSC) for autologous stem cell transplantion (ASCT) in patients with non-Hodgkin's lymphoma (NHL). In this analysis, we compare 12-month graft durability among NHL patients receiving P + G as a front-line or rescue mobilization regimen. Methodology: Patients enrolled in the Phase III study who failed to mobilize ≥2 × 106 CD34+ cells/kg could enter into the rescue arm of the study and receive P + G. Following a rest period of ≥7 days, patients were re-mobilized with G-CSF (10 mcg/kg/day) for four days, and on the evening of day four, plerixafor (240 mcg/kg SQ) was administered. On day five, all patients received a morning dose of G-CSF before apheresis. The apheresis was a 3 volume ± 10% apheresis. Patients continued to receive P + G followed by daily apheresis for up to four days or until ≥5 × 106 CD34+ cells/kg were collected. Graft durability was measured at 3, 6 and 12 months; grafts were considered durable if at least 2 of the 3 following criteria were met: platelet count >50,000/μl without transfusion for at least 2 weeks prior to follow-up, hemoglobin level ≥ 10 g/dL with no erythropoietin support or transfusions for at least 1 month before follow-up, absolute neutrophil count >1,000/μl with no G-CSF for at least 1 week before follow-up visit. Patients who had disease progression or died with a stable graft were censored. Results: As reported before, 130/150 (87%) patients receiving P + G as a front-line regimen and 37/62 (60%) receiving P + G as a rescue regimen collected ≥2 × 106 CD34+ cells/kg. 135 patients in the front-line group and 52 patients in the rescue group underwent ASCT. Data to evaluate graft durability at 12-months were available for 112/135 (83%) patients in the front-line group and 44/52 (85%) patients in the rescue group. At 12-months, the proportion of patients that maintained a durable graft in the front-line group was 98.2%. One patient had graft failure due to pre-existing myelodysplastic syndrome and one patient had AML. Comparatively, based on laboratory and clinical criteria, 100% of rescue patients maintained a durable graft at 12-months. Conclusion: These data demonstrate that the quality of the HSC collected with P + G in the rescue arm resulted in graft durability rates that were comparable to cells transplanted when P + G was used as a front-line mobilization regimen among patients with NHL.