ICIs target programmed cell death-1 (PD-1), PD ligand-1 (PD-L1), and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), with a subsequent disruption of the host T cell signaling and the upregulation of the T cell immune innate and adaptive response against cancer cells [28]. Here, CTLA4 is linked to cancer.