Immune checkpoint inhibitors (ICIs) such as monoclonal antibodies against cytotoxic T lymphocyte antigen-4 (CTLA-4), programmed cell death (PD-1), and the programmed death-ligand (PD-L1) are effective against several cancers, such as melanoma, non-small-cell lung carcinomas, renal cell carcinomas, and Hodgkin's lymphoma, amongst others [1–3]. Here, CTLA4 is linked to cancer.