Peripheral blood stem and progenitor cell collection in pediatric candidates for ex vivo gene therapy: a 10-year series.

Abstract Hematopoietic stem and progenitor cell (HSPC)-based gene therapy (GT) requires the collection of a large number of cells. While bone marrow (BM) is the most common source of HSPCs in pediatric donors, the collection of autologous peripheral blood stem and progenitor cells (PBSCs) is an attractive alternative for GT. We present safety and efficacy data of a 10-year cohort of 45 pediatric patients that underwent PBSC collection for backup and/or purification of CD34+ cells for ex vivo gene transfer. Median age was 3.7 years and median weight 15.8 kg. After mobilization with lenograstim/plerixafor (n=41) or lenograstim alone (n=4), and 1-3 cycles of leukapheresis, median collection was 37 x106 CD34+ cells/kg. The procedures were well tolerated. Patients that collected ≥7 and ≥13 x106 CD34+ cells/kg in the first cycle had pre-apheresis circulating counts of at ≥42 and ≥86 CD34+ cells/μL respectively. Weight-adjusted CD34+ cell yield was positively correlated with peripheral CD34+ cell counts, and influenced by female gender, disease and drug dosage. All patients received a GT product above the minimum target, ranging from 4 to 30.9 x106 CD34+ cells/kg. Pediatric PBSC collection compares well to BM harvest in terms of CD34+ cell yields for the purpose of GT, with a favorable safety profile.