PDCD1 and melanoma: More recently, immune checkpoint inhibitors (CPIs) that target the cytotoxic T-lymphocyte-associated protein 4 (CTLA4) and the program cell death protein 1 (PD-1) or its ligand PD-L1 have shown durable clinical responses across various cancer types, including melanoma, non-small cell lung cancer (NSCLC), locally advanced or metastatic urothelial carcinoma (mUC), and renal cell carcinoma (RCC)1,2.