Priming of hematopoietic progenitor cells by plerixafor and filgrastim in children with previous failure of mobilization with chemotherapy and/or cytokine treatment.

Plerixafor has been recently approved by the European Medicines Agency for adult patients who have failed other mobilization strategies. Experience in children, however, is extremely limited. We describe the experience of the use of this drug in 8 children under a compassionate-use program in 3 Italian and 2 Spanish centers. Plerixafor was generally well tolerated; only 2 of 8 children reported adverse effects, and these were mild in intensity. Peripheral blood progenitor cell priming was improved with plerixafor in 6 of 8 patients. In the remaining 2 patients, the target CD34+ cell count was below the target of 2 × 10(6) cells/kg, although in these patients cell counts before collection were good enough for leukapheresis. Plerixafor, therefore seems to be safe and effective for peripheral blood progenitor cell mobilization in children. Adverse events were comparable with those described with filgrastim alone.