{"classes":[{"categories":[{"measurements":[{"groupId":"OG000","value":"2"},{"groupId":"OG001","value":"1"}]}],"title":"Pre-existing"},{"categories":[{"measurements":[{"groupId":"OG000","value":"4"},{"groupId":"OG001","value":"2"}]}],"title":"Treatment-emergent"}],"denoms":[{"counts":[{"groupId":"OG000","value":"221"},{"groupId":"OG001","value":"109"}],"units":"Participants"}],"description":"Number of participants with positive ADA prior to taking study drug and/or during study. A participant was counted as \"treatment-emergent\" if there was a positive post-baseline sample while the baseline sample was ADA negative, or there was a positive post-baseline sample with a titer ≥ 4-fold of the baseline titer while the baseline sample was ADA positive. A participant was counted as \"preexisting\" if the baseline sample was ADA positive and the participant was not qualified for \"treatment-emergent.\"","groups":[{"description":"Luspatercept (ACE-536) was administered subcutaneously (SC) at a starting dose level of 1 mg/kg once every 21 days. Participants could be dose-titrated to 1.25 mg/kg, but the maximum total dose should not exceed 120 mg, total dose per administration during the Treatment Period, the Long-term Treatment Period, and Open-Label Treatment Period. BSC = Best Supportive Care","id":"OG000","title":"Luspatercept + BSC"},{"description":"Placebo (normal saline) was administered subcutaneously (SC) in volumes to match active treatment once every 21 days. BSC = Best Supportive Care","id":"OG001","title":"Placebo + BSC"}],"paramType":"COUNT_OF_PARTICIPANTS","populationDescription":"All treated participants with available measurements","reportingStatus":"POSTED","timeFrame":"Timeframe: pre-dose, Day 1, Days 22, 64, 106, 148, 232, 316","title":"Participants With Pre-Existing and/or Treatment-Emergent Antidrug Antibodies (ADA)","type":"SECONDARY","unitOfMeasure":"Participants"}