Peripheral Blood Stem Cell Collection for Sickle Cell Disease (SCD) Patients Using Plerixafor

The constitution of blood relies upon hematopoietic stem cells (HSCs), which stay in the bone marrow and differentiate to all lineages of peripheral blood cells. HSC transplantation is the only curative option currently available for sickle cell disease (SCD) patients either via allogeneic HSC transplantation or HSC-targeted gene therapy. Granulocyte-colony stimulating factor (G-CSF)- mobilized HSCs are frequently utilized in the adult setting of HSC transplantation because of the faster hematologic recovery as compared to bone marrow. As an autologous HSC source for gene therapy, bone marrow harvest has been generally employed since G-CSF has been prohibitive in SCD patients due to granulocyte stimulation and the associated reports of vaso-occlusive crises, multi-organ failure, and death. However, when bone marrow harvest is used, the amounts of collected cells are limited and anesthesia is required. In order to obtain HSCs in large numbers without anesthesia, patients will undergo mobilization followed by large volume apheresis. Plerixafor is an alternative treatment for mobilization without direct stimulation to granulocytes, and it is theoretically applicable for SCD patients. The primary endpoint of this study is to obtain sufficient amounts of HSCs collected from the peripheral blood in SCD patients after plerixafor mobilization with an acceptable safety profile. The harvested products will be stored as backup for patients undergoing gene therapy as well as allogeneic HSC transplantation.