Nivolumab for High-Risk MDS/AML Patients After Allogeneic Stem Cell Transplant With Post-Transplant Cyclophosphamide

At Day +50 (±10 days) post-allogeneic SCT, participants will be treated with Nivolumab. Nivolumab will be administered intravenously once every two weeks for a total of 4 treatments. Participants will initially receive nivolumab at a significantly reduced starting dose of 0.25 mg/kg. This dose was determined based on the incidence of increased aGVHD, which was noted after treatment post-SCT in previous studies. Nivolumab IV will be given every 2 weeks for 4 cycles. One dose of nivolumab is equivalent to one cycle. The first administration will be at Day +50 (±10 days), assuming the participant has not had any evidence of Grade II-IV aGVHD after allogeneic SCT and does not have any current evidence of any grade of aGVHD at the day of first application of nivolumab. Depending on emerging safety data, dose escalation cohorts will explore higher dose levels of nivolumab at 0.5 mg/kg and 1 mg/kg.