PDCD1 and metastatic melanoma: The approval of ipilimumab—the archetype anti-CTLA-4 monoclonal antibody (mAb)—by the US Food and Drug Administration (FDA) for treatment of metastatic melanoma in 2011 paved the way for the approval of seven additional ICPis—four anti-PD-1 (nivolumab, pembrolizumab, cemiplimab, dostarlimab) and three anti-PD-L1 (atezolizumab, durvalumab, avelumab,) monoclonal antibodies (mAbs) by the FDA—as of 14 November 2022, to revolutionize the treatment of an increasing list of malignancies [5].