Immune checkpoint inhibitors (ICIs) appear today as the cornerstone of immunotherapy in several cancer types and are mainly represented by antibodies targeting anti-programmed cell death protein 1 (PD-1), anti-programmed cell death ligan-1 (PD-L1), and anti-cytotoxic T-lymphocyte antigen-4 (CTLA-4). Here, PDCD1 is linked to cancer.