PDCD1 and acute myeloid leukemia: However, there is still promise for the combination of PD1 blockade and HMA, as results from the Phase II trial investigating nivolumab and azacitidine in relapsed/refractory AML yielded a 33% overall response rate, with a higher response rate in HMA naïve vs. HMA pre-treated patients (58% vs. 22%)[63].