CTLA4 and melanoma: Currently, the four FDA-approved immunotherapies for melanoma (nivolumab and pembrolizumab, which target PD-1; ipilimumab, which targets CTLA-4; and opdualag, which targets PD-1 and LAG-3 [114,115,116,117,142,143]) all function as immune checkpoint inhibitors, counteracting the immunosuppressive effects of T cell exhaustion in the tumour microenvironment [144,145,146,147].