Mobilization of Leukemic Cells Using Plerixafor as Part of a Myeloablative Preparative Regimen for Patients with Acute Myelogenous Leukemia Undergoing Allografting: Assessment of Safety and Tolerability.

Allogeneic hematopoietic cell transplantation (HCT) is potentially curative for acute myelogenous leukemia (AML); however, a major cause of treatment failure is disease relapse. The purpose of this single-center Phase I study was to determine the safety and tolerability of administration of the CXCR4 inhibitor plerixafor (Mozobil; Sanofi Genzyme) along with myeloablative conditioning in patients with AML undergoing allogeneic HCT. The rationale was that plerixafor may mobilize leukemic stem cells, making them more susceptible to the conditioning chemotherapy (registered at ClinicalTrials.gov; identifier NCT01141543). Three patients were enrolled into each of 4 sequential cohorts (12 patients total). Patients in the first cohort received 1 dose of plerixafor (240 μg/kg s.c.) before the first dose of fludarabine and busulfan, and subsequent cohorts received injections before 2, 3, and 4 days of conditioning chemotherapy. The median age at HCT was 49 years (range, 38 to 58 years). All patients engrafted following HCT, with an absolute neutrophil count ≥.5 × 109/L observed at a median of 14 days (range, 11 to 18 days). Adverse events possibly related to plerixafor were transient and not severe. Main adverse events following the injection were nausea and dizziness in 4 patients (33%) and fatigue in 4 patients (33%). Among the 12 patients, 2 patients (17%) relapsed post-HCT and 6 (50%) were alive at the last follow-up. The median follow-up of survivors was 67 months (range, 53 to 82 months). In conclusion, plerixafor administration is safe and well tolerated when included in a myeloablative conditioning regimen for allogeneic HCT for AML. Further study in a larger cohort is warranted for the investigation of the impact of plerixafor on post-allogeneic HCT outcomes.