Safety and Efficacy of Plerixafor for Mobilization of Peripheral Blood Stem Cells in Pediatric Patients

Background: Chemotherapy followed by filgrastim is the most common strategy used to mobilize cells for high dose chemotherapy and autologous stem cell transplantation. Unfortunately, this method does not always lead to adequate cell collection in heavily pretreated patients with relapsed malignancies or if multiple transplants are required. Plerixafor is an agent that has been studied in adults and has been shown to be safe and efficacious in the mobilization of peripheral blood stem cells (PBSC). Plerixafor is hematopoietic stem cell mobilizer which inhibits the CXCR4 chemokine receptor and blocks binding of its cognate ligand, stromal cell-derived factor-1-alpha (SDF-1-alpha) which results in leukocytosis and elevations in circulating hematopoietic progenitor cells. Despite its use in adults, little evidence exists to support its use in children. Here we report our observations of 11 children at Cincinnati Children’s Hospital Medical Center (CCHMC) who received plerixafor to mobilize PBSC.

Methods: A retrospective review of all patients receiving plerixafor as part of their mobilization regimen at CCHMC between January 2011 and September 2013 was conducted. All patients receiving at least one dose were included. Data on the number of plerixafor doses administered, cells collected, and adverse events related to plerixafor were collected.

Results: Eleven patients received plerixafor during the designated time period; 9/11 patients (81.8%) had relapsed malignancies and 2/11 patients (18.2%) required 3 and 4 autologous stem cell transplants for brain tumors. The median age of patients receiving plerixafor was 6 years (range 3-15 years). All patients were given 0.24 mg/kg of plerixafor and the median number of plerixafor doses received was 3 (range 1-4 doses). Collection target was 1x10⁶ of CD34+cells/kg for each transplant. An adequate number of CD34+ cells were obtained in 9 of 11 patients (81.8%).  The median number of CD34+ cells collected for patients who reached collection goal was 5.7x 10⁶/kg (range 1.3-12.4 x 10⁶/kg). No acute adverse events were noted to be attributable to plerixafor administration.

Conclusion: Our findings suggest that plerixafor use in children is safe and efficacious for the mobilization of PBSCs in children with relapsed malignancies or requiring stem cells for multiple transplants.