{"groups":[{"description":"Sotatercept 0.1 mg/kg administered via subcutaneous injection every third week (Q3W). Participants were randomized to either the 0.1 mg/kg arm or the 0.3 mg/kg arm. Efficacy and safety data were assessed by a Steering Committee. Based upon the occurrence of dose-limiting toxicity (DLT) in ≤ 1/5 subjects in Cycle 1 in the 0.1 mg/kg and 0.3 mg/kg treatment groups, the 0.5 mg/kg treatment group began inclusion in the randomization scheme.","id":"FG000","title":"Sotatercept 0.1 mg/kg"},{"description":"Sotatercept 0.3 mg/kg administered via subcutaneous injection every third week (Q3W). Participants were randomized to either the 0.1 mg/kg arm or the 0.3 mg/kg arm. Efficacy and safety data were assessed by a Steering Committee. Based upon the occurrence of dose-limiting toxicity (DLT) in ≤ 1/5 subjects in Cycle 1 in the 0.1 mg/kg and 0.3 mg/kg treatment groups, the 0.5 mg/kg treatment group began inclusion in the randomization scheme.","id":"FG001","title":"Sotatercept 0.3 mg/kg"},{"description":"Sotatercept 0.5 mg/kg administered via subcutaneous injection every third week (Q3W). Participants were randomized to one of the active treatment arms. Efficacy and safety data were assessed by a Steering Committee. Based upon the occurrence of dose-limiting toxicity (DLT) in ≤ 1/6 subjects in Cycle 1 in the 0.5 mg/kg treatment group, the 1.0 mg/kg treatment group began inclusion in the randomization scheme.","id":"FG002","title":"Sotatercept 0.5 mg/kg"},{"description":"Sotatercept 1.0 mg/kg administered via subcutaneous injection every third week (Q3W). Participants were randomized to one of the active treatment arms. Efficacy and safety data were assessed by a Steering Committee. Based upon the occurrence of dose-limiting toxicity (DLT) in ≤ 1/6 subjects in Cycle 1 in the 1.0 mg/kg treatment group, the 2.0 mg/kg treatment group began inclusion in the randomization scheme. Following evaluation of all treatment group data by the Steering Committee, enrollment continued only in the 1.0 mg/kg arm because the arm had the greatest frequency of erythroid hematological improvement (HI-E).","id":"FG003","title":"Sotatercept 1.0 mg/kg"},{"description":"Sotatercept 2.0 mg/kg administered via subcutaneous injection every third week (Q3W). Participants were randomized to one of the active treatment arms. Efficacy and safety data were assessed by a Steering Committee. The 2.0 mg/kg sotatercept dose was reduced to 1.5 mg/kg for ongoing and newly enrolled participants by protocol amendment.","id":"FG004","title":"Sotatercept 2.0 mg/kg"}],"periods":[{"dropWithdraws":[{"reasons":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"0"},{"groupId":"FG002","numSubjects":"2"},{"groupId":"FG003","numSubjects":"1"},{"groupId":"FG004","numSubjects":"0"}],"type":"Disease Relapse"},{"reasons":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"2"},{"groupId":"FG002","numSubjects":"2"},{"groupId":"FG003","numSubjects":"3"},{"groupId":"FG004","numSubjects":"2"}],"type":"Adverse Event"},{"reasons":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"0"},{"groupId":"FG002","numSubjects":"3"},{"groupId":"FG003","numSubjects":"1"},{"groupId":"FG004","numSubjects":"1"}],"type":"Withdrawal by Subject"},{"reasons":[{"groupId":"FG000","numSubjects":"7"},{"groupId":"FG001","numSubjects":"4"},{"groupId":"FG002","numSubjects":"13"},{"groupId":"FG003","numSubjects":"20"},{"groupId":"FG004","numSubjects":"1"}],"type":"Lack of Therapeutic Effect"},{"reasons":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"0"},{"groupId":"FG002","numSubjects":"0"},{"groupId":"FG003","numSubjects":"1"},{"groupId":"FG004","numSubjects":"0"}],"type":"Progressive Disease"},{"reasons":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"0"},{"groupId":"FG002","numSubjects":"1"},{"groupId":"FG003","numSubjects":"9"},{"groupId":"FG004","numSubjects":"1"}],"type":"Other"}],"milestones":[{"achievements":[{"groupId":"FG000","numSubjects":"7"},{"groupId":"FG001","numSubjects":"6"},{"groupId":"FG002","numSubjects":"21"},{"groupId":"FG003","numSubjects":"35"},{"groupId":"FG004","numSubjects":"5"}],"type":"STARTED"},{"achievements":[{"comment":"\\# who completed treatment","groupId":"FG000","numSubjects":"0"},{"comment":"\\# who completed treatment","groupId":"FG001","numSubjects":"0"},{"comment":"\\# who completed treatment","groupId":"FG002","numSubjects":"0"},{"comment":"\\# who completed treatment","groupId":"FG003","numSubjects":"0"},{"comment":"\\# who completed treatment","groupId":"FG004","numSubjects":"0"}],"type":"COMPLETED"},{"achievements":[{"groupId":"FG000","numSubjects":"7"},{"groupId":"FG001","numSubjects":"6"},{"groupId":"FG002","numSubjects":"21"},{"groupId":"FG003","numSubjects":"35"},{"groupId":"FG004","numSubjects":"5"}],"type":"NOT COMPLETED"}],"title":"Overall Study"}],"preAssignmentDetails":"Enrollment in the other arms (sotatercept 0.5, 1.0 and 2.0 mg/kg arms) commenced after the Steering Committee approved the higher doses based on the safety of preceding doses.","recruitmentDetails":"Participants were stratified by concentration of serum erythropoietin (EPO) (\\<500 versus ≥500 IU/L), by number of transfusions within 56 days of study enrollment (\\<4 versus ≥4 units of red blood cells) and assigned randomly to 0.1 mg/kg and 0.3 mg/kg arms."}