This is a single-arm, open-label, multi-site, single-dose Phase 1/2/3 study in subjects with severe sickle cell disease (SCD). The study will evaluate the safety and efficacy of autologous CRISPR-Cas9 Modified CD34+ Human Hematopoietic Stem and Progenitor Cells (hHSPCs) using CTX001.
Key Inclusion Criteria: * Diagnosis of severe sickle cell disease as defined by: * Documented severe sickle cell disease genotype * History of at least two severe vaso-occlusive crisis events per year for the previous two years prior to enrollment * Eligible for autologous stem cell transplant as per investigators judgment Key Exclusion Criteria: * An available 10/10 human leukocyte antigen (HLA)-matched related donor * Prior hematopoietic stem cell transplant (HSCT) * Clinically significant and active bacterial, viral, fungal, or parasitic infection Other protocol defined inclusion/exclusion criteria may apply