ICB is a specific type of IT using drugs called immune checkpoint inhibitors to block inhibitory molecules on immune cells, known as immune checkpoints (e.g., programmed cell death protein 1 (PD‐1) and cytotoxic T‐lymphocyte‐associated protein 4 (CTLA‐4), etc.).[189] Immune checkpoints are able to regulate immune responses and prevent excessive immune activation, but cancer cells can hijack these checkpoints to evade immune detection and attack. The gene discussed is PDCD1; the disease is cancer.