SCD Stem Cell Mobilization and Apheresis Using Motixafortide

Inclusion Criteria: * Participants with severe sickle cell disease (SCD) who are ≥18 years of age and willing to donate autologous hematopoietic stem cells (HSCs) for advancing future gene therapy for SCD after collection of back-up product. Severe SCD, for the purpose of this study, will be defined as participants who are receiving chronic transfusion therapy due to SCD related complications or are eligible for or currently enrolled on an allogeneic transplant protocol. * Participant must have a documented diagnosis of SCD with documentation of SCD genotype by medical history * Participants should either have a central line in place, be able to undergo apheresis without the necessity of the insertion of a central venous catheter, or agree to have a central line placed if IV access is inadequate. * ECOG performance status/Karnofsky score/Lansky score \>80 * White blood cell (WBC) count \>3.0 x 10\^9/L, absolute neutrophil count (ANC) \>1.0 x 10\^9/L, and platelet count \>150 x 10\^9/L, and hemoglobin \>7.0 gm/dL * Adequate renal function defined as serum/plasma creatinine \< 1.5 mg/dL and an estimated glomerular filtration rate (eGFR) of at least 60 mL/min/1.73 m\^2 based on the CKD-Epi equation or the St. Jude equation. * Adequate liver function defined as direct bilirubin \< 2.5 times the upper limit of normal range; aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \< 5 times the upper limit of normal range. * Participant's cardiac function (i.e., ejecti…