Cytotoxic T lymphocyte-associated molecule-4 (CTLA-4), programmed cell death receptor-1 (PD-1), and programmed cell death ligand-1 (PD-L1) are checkpoints of immune-inhibitory pathways and antibodies against CTLA-4, PD-1, and PD-L1 that have all been approved for the treatment of several types of cancers by the US Food and Drug Administration [9,10]. Here, CTLA4 is linked to cancer.