The purpose of this study is to evaluate the safety, tolerability, and efficacy of treatment with EDIT-301 in adult participants with Transfusion Dependent beta Thalassemia

This is a Phase 1/2 single-arm, open-label, multicenter study evaluating the safety, tolerability, and efficacy of a single unit dose of EDIT-301 for autologous hematopoietic stem cell transplant in adult participants with TDT, age 18 to 35 years, inclusive

Key Inclusion Criteria:

Diagnosis of Transfusion Dependent B-Thalassemia as defined by:

• Documented homozygous β-thalassemia or compound heterozygous β-thalassemia including β-thalassemia/hemoglobin E (HbE) based on historical data in medical records, and
• History of at least 100 mL/kg/year or 10 U/year of packed red blood cell (RBC) transfusions in the 2 years prior to signing informed consent
• Clinically stable and eligible to undergo autologous HSCT
• Karnofsky Performance Status ≥ 70

Key Exclusion Criteria:

• Available 10/10 human leukocyte antigen (HLA)-matched related donor
• Prior HSCT or contraindications to autologous HSCT
• Participants with associated a history of α-thalassemia and > 1 alpha chain deletion, or alpha multiplications as documented in medical records
• Participants with a history of other inherited hemoglobinopathy or thalassemic mutation (Hb S, C, D or other) as documented in medical records
• Prior receipt of gene therapy
• Inadequate bone marrow function, as defined by white blood cell count of < 3 x 10^9/L or a platelet count < 100 x 10^9/L (without hypersplenism), per investigator judgement
• Inadequate organ function
• Advanced liver disease
• Any prior or current malignancy, or immunodeficiency disorder,
• Immediate family member with a known or suspected Familial Cancer Syndrome
• Clinically significant and active bacterial, viral, fungal, or parasitic infection