A Study to Assess the Safety, Tolerability, and Efficacy of ST-400 for Treatment of Transfusion-Dependent Beta-thalassemia (TDT)

Once consented, study participants will progress through the following stages: * Screening: in-person visit at the study site to confirm eligibility for proceeding * Collection: autologous (self) blood stem cells are harvested at the study site, also known as apheresis * Manufacturing of ST-400: no study participant activities expected * Infusion: conditioning chemotherapy, followed by infusion of ST-400, occurs at the study site * Follow-up: follow up at the study site to monitor for safety and effectiveness of the study