CTLA4 and cancer: In recent years, the development of antibodies that target immune checkpoint proteins, including PD-1, PD-L1, and cytotoxic T lymphocyte-associated antigen-4, has led to a paradigm shift in cancer treatment and the US Food and Drug Administration approval of numerous therapeutics of this type, including for nivolumab, pembrolizumab, ipilimumab, and atezolizumab (17).