The programmed cell death 1 (PD-1) inhibitor pembrolizumab and the cytotoxic T-lymphocyte-associated protein 4 (CTLA4) inhibitor, ipilimumab, have been both studied in phase Ib/II trials in patients with intermediate/high-risk MDS who failed HMA showing limited efficacy in monotherapy (interim analysis for pembrolizumab, NCT03094637) [125,126]. This evidence concerns the gene CTLA4 and myelodysplastic syndrome.