Successful hematopoietic stem cell mobilization and apheresis collection using plerixafor alone in sickle cell patients

Abstract

Novel therapies for sickle cell disease (SCD) based on genetically engineered autologous hematopoietic stem and progenitor cells (HSPCs) are critically dependent on a safe and effective strategy for cell procurement. We sought to assess the safety and efficacy of plerixafor when used in transfused patients with SCD for HSC mobilization. Six adult patients with SCD were recruited to receive a single dose of plerixafor, tested at lower than standard (180 µg/kg) and standard (240 µg/kg) doses, followed by CD34+ cell monitoring in peripheral blood and apheresis collection. The procedures were safe and well-tolerated. Mobilization was successful, with higher peripheral CD34+ cell counts in the standard vs the low-dose group. Among our 6 donors, we improved apheresis cell collection results by using a deep collection interface and starting apheresis within 4 hours after plerixafor administration. In the subjects who received a single standard dose of plerixafor and followed the optimized collection protocol, yields of up to 24.5 × 106 CD34+ cells/kg were achieved. Interestingly, the collected CD34+ cells were enriched in immunophenotypically defined long-term HSCs and early progenitors. Thus, we demonstrate that plerixafor can be employed safely in patients with SCD to obtain sufficient HSCs for potential use in gene therapy.

Curative options for sickle cell disease: haploidentical stem cell transplantation or gene therapy?

“…In 2016, the HGB‐206 protocol was modified for Group B to increase DP vector copy number (VCN), require preharvest transfusions, increase target busulfan levels, and in Group C, explore the use of plerixafor for mobilization and apheresis for cell collection. Reports suggest higher CD34 + cells/kg yield after plerixafor mobilization, improved transduction efficiency, and improved HSC quality compared to BM from subjects with SCD (Uchida et al , ; Tisdale et al , ; Boulad et al , ; Esrick et al , ; Lagresle‐Peyrou et al , ; Leonard et al , ). In HGB‐206, a median CD34 + yield was reported of 4·3 (0·1–10·8) × 10 6 and 10·4 (3·8–21·6) × 10 6 cells/kg (Mapara et al , ).…”

“…Erythroid‐specific expression of microRNA‐adapted shRNAs (shRNAmiR) targetting BCL11A effectively induced HbF in human erythroid cells derived from transduced HSCs (Brendel et al , ) and is currently being investigated (NCT03282656). In the first cohort of patients ≥18 years old, 3·3–6·7 × 10 6 CD34 + cells/kg were collected in three patients after plerixafor mobilization and apheresis (Esrick et al , ). CD34 + cells were transduced with the shRNAmiR vector, demonstrating a VCN of 3·3–5·1 copies per cell and >95% vector‐positive CD34 + ‐derived colonies.…”

“…With regard to gene therapy, success is dependent on safely obtaining a sufficient quantity of autologous SCD patient HSCs capable of lifelong engraftment. In patients with SCD, steady‐state BM harvesting is associated with suboptimal HSC quality and yield (Leonard et al , ), and PB mobilization with granulocyte colony stimulating factor is contra‐indicated (Abboud et al , ; Adler et al , ; Fitzhugh et al , ) though single‐agent plerixafor mobilization appears to be safe and effective (Tisdale et al , ; Boulad et al , ; Esrick et al , ; Lagresle‐Peyrou et al , ). Some patients may be unable to tolerate stem cell collection due to high risk of anaesthesia and fluid shifts in a BM harvest or PB collection.…”

Gentherapie von Hämoglobinkrankheiten – aktuelle Konzepte und Herausforderungen

“…Die aus Knochenmark gewinnbare Stammzellmenge und vor allem die Kapazität der daraus gewonnenen Stammzellen zur β-Globin-Synthese ist limitiert [47 -49]. Aus diesem Grund wurde zuletzt alleinig Plerixafor zur Mobilisierung eingesetzt [50]. Die so gewonnenen Stammzellen zeigten nach Transduktion eine sehr gute Expression von β-Globin [47].…”

“…Dies und vor allem das genannte geringe Transduktionspotenzial von aus Knochenmark gewonnenen Stammzellen gaben den Ausschlag dafür, dass sich die Apherese aus peripherem Blut als Stammzellquelle durchgesetzt hat. Dabei gilt es, die Sammelstrategie an die spezifischen Sedimentationseigenschaften von hämatopoetischen Stammzellen im Blut von Patientinnen und Patienten mit Thalassämie anzupassen und einen deutlich höheren Erythrozytenanteil im Apheresat als sonst üblich zu akzeptieren [50].…”