PDCD1 and acute myeloid leukemia: Based on preclinical findings that demonstrate PD-1 and PD-L1 are upregulated in MDS and R/R AML, especially in patients developing resistance to HMAs, the efficacy of several monoclonal antibodies targeting this pathway as single agent or combination therapies in treatment-naïve and HMA-failure MDS or R/R AML patients has been assessed.