Specifically, programmed cell death 1 (PD-1), programmed cell death ligand 1 (PD-L1), and monoclonal antibodies against cytotoxic T lymphocyte antigen 4 (CTLA-4) have been approved in the first-line and second-line treatment of various malignant neoplasms, including non-small cell lung cancer (NSCLC), melanoma, renal cell carcinoma (RCC), etc. (1–4). Here, PDCD1 is linked to melanoma.