An Efficacy and Safety Study of Luspatercept (ACE-536) Versus Placebo in Subjects With Myeloproliferative Neoplasm-Associated Myelofibrosis on Concomitant JAK2 Inhibitor Therapy and Who Require Red Blood Cell Transfusions

Subjects must satisfy the following criteria to be randomized in the study: Inclusion Criteria \- Subject is ≥18 years of age at the time of signing the ICF. * Subject has a diagnosis of PMF according to the 2016 World Health Organization (WHO) criteria or diagnosis of post-ET or post-PV MF according to the IWG-MRT 2007 criteria, confirmed by the most recent local pathology report. * Subject is requiring RBC transfusions as defined as:. i) Average RBC-transfusion frequency: 4 to 12 RBC units/12 weeks immediately up to randomization. There must be no interval \> 6 weeks (42 days) without ≥ 1 RBC transfusion. ii) RBC transfusions are scored in determining eligibility when given for treatment of:. A. Symptomatic (ie, fatigue or shortness of breath) anemia with a pretransfusion Hgb ≤ 9.5 g/dL or. B. Asymptomatic anemia with a pretransfusion Hgb ≤ 7 g/dL. iii) RBC transfusions given for worsening of anemia due to bleeding or infections are not scored in determining eligibility. \- Subjects on continuous (eg, absent of dose interruptions lasting ≥ 2 consecutive weeks) JAK2 inhibitor therapy as approved in the country of the study site for the treatment for MPN-associated MF as part of their standard-of-care therapy for at least 32 weeks, on stable daily dose for at least 16 weeks immediately up to the date of randomization and anticipated to be on a stable daily dose of that JAK2 inhibitor for at least 24 weeks after randomization. * Subject has an Eastern Cooperative O…