PDCD1 and acute myeloid leukemia: Beyond antibody-based approaches, immune checkpoint inhibitors (e.g., Programmed cell death protein 1 (PD-1)/Programmed cell death ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors) have shown limited efficacy in relapsed/refractory AML, primarily due to immune evasion mechanisms such as PD-L1 upregulation and Treg-mediated immunosuppression [168,169].