Immune checkpoint inhibitors (ICIs) are monoclonal antibodies that interact with molecules like programmed cell death 1 (PD-1), programmed cell death 1 ligand 1 (c), or cytotoxic T lymphocyte antigen 4 (CTLA-4); so, these are molecules that allow cancer cells to remain unnoticed by infiltrating lymphocytes. Here, PDCD1 is linked to cancer.