• Adult participant≥ 18 years with documented diagnosis of A-Thal HbH disease with Transfusion dependence defined as:.

‣ TD participant: ≥ 6 RBC units during the 24 weeks prior to randomization.

⁃ NTD participant:\< 6 RBC units during the 24 weeks prior to randomization(transfusion due to conditions other than A-Thal will not be considered)and, RBC transfusion-free during at least 8 weeks prior to randomization(unless transfusion was required to treat an acute medical condition other than A-Thal) and, mean baseline Hb ≤ 10 g/dL, based on a minimum of 2 measurements ≥ 1 week apart within 4 weeks prior to randomization; hemoglobin values within 21 days post-transfusion will be excluded.

• Adult participant has Eastern Cooperative Oncology Group (ECOG) 34 score of 0 or 1.

• Adolescent participant 12 years to \< 18 years with documented diagnosis of A-Thal HbH disease with transfusion dependence defined as:.

‣ TD participant: ≥ 4 RBC events during the 24 weeks prior to enrollment and, no transfusion-free period for \> 56 days during the 24 weeks prior to enrollment. Participants must have a history of regular transfusions for at least 2 years.

⁃ NTD participant:\< 4 RBC events during the 24 weeks prior to enrollment and RBC transfusion-free during at least 8 weeks prior to enrollment and, mean baseline Hb ≤ 10 g/dL, based on a minimum of 2 measurements ≥ 1 week apart within 4 weeks prior to enrollment, hemoglobin values within 21 days post-transfusion will be excluded.

⁃ Participant has Karnofsky (age ≥16 years) or Lansky (age \< 16 years) performance status score ≥ 50 at screening.