A Study to Compare the Efficacy and Safety of Luspatercept (ACE-536) Versus Epoetin Alfa for the Treatment of Anemia Due to IPSS-R Very Low, Low, or Intermediate Risk Myelodysplastic Syndromes (MDS) Participants Who Require Red Blood Cell Transfusions and Are ESA Naïve

Inclusion Criteria

• Documented diagnosis of Myelodysplastic syndromes (MDS) according to WHO 2016 classification that meets revised international prognostic scoring system (IPSS-R) classification of very low, low, or intermediate risk disease, and have < 5% blasts in bone marrow
• Endogenous serum erythropoietin (sEPO) level of < 500 U/L
• Requires Red blood cell (RBC) transfusions, as documented by the criteria: Average transfusion requirement of 2 - 6 units/8 weeks of packed red blood cells (pRBCs) confirmed for a minimum of 8 weeks immediately preceding randomization
• Eastern Cooperative Oncology Group (ECOG) score of 0, 1, or 2

Exclusion Criteria

• Clinically significant anemia due to iron, vitamin B12, or folate deficiencies, or autoimmune or hereditary hemolytic anemia, or hypothyroidism, or any type of known clinically significant bleeding or sequestration or drug induced anemia
• Known history of diagnosis of Acute myeloid leukemia (AML)
• Uncontrolled hypertension, defined as repeated elevations of systolic blood pressure (SBP) of ≥ 150 mmHg and/or diastolic blood pressure (DBP) ≥ 100 mmHg despite adequate treatment Other protocol-defined inclusion/exclusion criteria apply