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. Safety and tolerability of EDIT-301 will be assessed in the proportion of participants achieving engraftment and the frequency and severity of AEs (incidence of adverse events and grade 3 or higher serious adverse events. 

Study treatment consists of CD34+ mobilization, myeloablative conditioning, administration of EDIT-301 and 2 years of follow up.

EDIT-301 is a one-time intravenous infusion of cell therapy product consisting of autologous CD34 +HSPC, edited at the γ-globin gene (HBG1 and HBG2) promoters by a clustered regularly interspaced short palindromic repeats (CRISPR)-Cas12a ribonucleoprotein (RNP). The total duration of the study for each participant is up to approximately 30 months from the time of informed consent to the end of study visit (including 24 months of post-treatment follow-up). EDIT-301 is also being evaluated in participants with Severe Sickle Cell Disease.