CTLA4 and metastatic melanoma: Since March 2011, when ipilimumab, a monoclonal antibody (mAb) directed against cytotoxic lymphocyte-associated protein 4 (CTLA-4), became the first FDA-approved ICI for patients with advanced/metastatic melanoma, numerous mAbs targeting other checkpoints (like PD-1 and PD-L1) have been implemented as another pillar in cancer clinical practice, providing durable responses in a wide array of solid malignancies.