A Study Evaluating the Efficacy and Safety of Mitapivat in Participants With Transfusion-Dependent Alpha- or Beta-Thalassemia (α- or β-TDT)

Inclusion Criteria: * Greater than or equal to (≥)18 years of age at the time of providing informed consent; * Documented diagnosis of thalassemia (β-thalassemia with or without α-globin gene mutations, hemoglobin E (HbE)/β-thalassemia, or α-thalassemia/hemoglobin H (HbH) disease) based on deoxyribonucleic acid (DNA) analysis; * Considered transfusion-dependent, defined as 6 to 20 red blood cells (RBC) units transfused and ≤6-week transfusion-free period during the 24-week period before randomization; * If taking hydroxyurea, the hydroxyurea dose must be stable for ≥16 weeks before randomization; * Women of childbearing potential (WOCBP) must be abstinent of sexual activities that may induce pregnancy as part of their usual lifestyle or agree to use two forms of contraception, one of which must be considered highly effective, from the time of providing informed consent, throughout the study, and for 28 days after the last dose of study drug. The second form of contraception can be an acceptable barrier method; * Written informed consent before any study-related procedures are conducted and willing to comply with all study procedures for the duration of the study. Exclusion Criteria: * Pregnant, breastfeeding, or parturient; * Documented history of homozygous or heterozygous sickle hemoglobin (Hb S) or hemoglobin C (Hb C); * Prior exposure to gene therapy or prior bone marrow or stem cell transplantation; * Currently receiving treatment with luspatercept; the last dose must…