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:

1. 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.
2. 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
3. Eastern Cooperative Oncology Group (ECOG) score of 0, 1, or 2

Exclusion Criteria:

1. Prior therapy with disease modifying agents for underlying MDS disease
2. Known clinically significant anemia due to iron, vitamin B12, or folate deficiencies, or autoimmune or hereditary hemolytic anemia, or gastrointestinal bleeding
3. 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