PDCD1 and melanoma: Anti-PD-1/PD-L1 mAbs, such as pembrolizumab, nivolumab, and cemiplimab (anti-PD-1), along with atezolizumab, avelumab, and durvalumab (anti-PD-L1), inhibit this pathway to augment CD8+ T-cell function, resulting in tumor regression in melanoma, renal cell carcinoma, non-small cell lung cancer (NSCLC), and bladder cancer; similarly, ipilimumab, an anti-CTLA-4 mAb, improves outcomes in melanoma and hepatocellular carcinoma (HCC) by activating T-cell responses and reducing immunosuppressive components such as Tregs and myeloid-derived suppressor cells (MDSCs) [40–46].