A Study to Evaluate the Efficacy, Drug Levels and Safety of Luspatercept (ACE-536) for the Treatment of Anemia Due to IPSS-R Very Low, Low, or Intermediate Risk Myelodysplastic Syndromes in Chinese and Japanese Participants With Ring Sideroblasts Who Require Red Blood Cell Transfusions

Inclusion Criteria: * Refractory or intolerant to, or ineligible for, prior Erythropoiesis stimulating agent (ESA) treatment as defined by any one of the following: Refractory to prior ESA treatment, Intolerant to prior ESA treatment, or ESA ineligible. * previously treated with an ESA or granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, both agents must have been discontinued ≥ 4 weeks prior to date of luspatercept treatment * Eastern Cooperative Oncology Group (ECOG) score of 0, 1, or 2 Exclusion Criteria: * Prior therapy with disease modifying agents for underlying MDS disease * Known clinically significant anemia due to iron, vitamin B12, or folate deficiencies, or autoimmune or hereditary hemolytic anemia, or gastrointestinal bleeding * Serum aspartate aminotransferase/serum glutamic oxaloacetic transaminase (AST/SGOT) or alanine aminotransferase/serum glutamic pyruvic transaminase (ALT/SGPT) ≥ 3.0 x upper limit of normal (ULN) Other protocol-defined inclusion/exclusion criteria apply