Moreover, anti-tumor immune responses are commonly boosted by mAb-based inactivation of immunosuppressive checkpoint molecules [PD-1/PD-L1, cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), lymphocyte activation gene-3 (LAG-3), T cell immunoglobulin and mucin-domain containing-3 (TIM-3), T cell immunoglobulin and ITIM domain (TIGIT), V-domain Ig suppressor of T cell activation (VISTA), etc.], which are known to suppress the activation and function of T cells and downregulate immune (including anti-cancer) reactivity [4,18]. Here, CTLA4 is linked to cancer.