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.