A Study to Evaluate Luspatercept (ACE-536) in Chinese Participants Who Require Regular Red Blood Cell Transfusions Due to Beta (β)-Thalassemia.

Prior treatment

• Participant has a history of deep venous thrombosis or stroke or thromboembolic events (venous or arterial) requiring medical intervention ≤24 weeks prior to randomization.
• Participant uses chronic anticoagulant therapy, unless the treatment stopped at least 28 days prior to randomization. Anticoagulant therapies used for prophylaxis for surgery or high-risk procedures as well as low-molecular-weight heparin for superficial venous thrombosis and chronic aspirin are allowed.
• Participant used immunomodulatory imide drugs (IMiDs) ≤ 24 weeks prior to randomization

Other illness

• Participant has active hepatitis C virus (HCV) infection as demonstrated by a positive HCVribonucleic acid (RNA) test of sufficient sensitivity, or active infectious hepatitis B virus (HBV) as demonstrated by the presence of hepatitis B surface antigen (HBsAg) and/or HBVdeoxyribonucleic acid (DNA) positive, or known positive human immunodeficiency virus (HIV).

Lab values

• Participant has a diagnosis of Hemoglobin S/β-thalassemia or α-thalassemia (for example, Hemoglobin H).

Other

• Participant who has EMH complications requiring treatment to control the growth of EMH mass(es) during the screening period.

• Participant is willing and able to adhere to the study visit schedule (for example, not scheduled to receive hematopoietic stem cell transplantation \[HSCT\]) and other protocol requirements.
• Participant has documented diagnosis of β-thalassemia or Hemoglobin E/β-thalassemia (β-thalassemia with mutation and/or multiplication of alpha (α) globin is allowed).
• Participant is regularly transfused, defined as: 6-25 RBC units in the 24 weeks prior to randomization and no transfusion-free period for \>42 days during that period.
• Participant has Eastern Cooperative Oncology Group (ECOG) score of 0 or 1.