CTLA4 and melanoma: Ipilimumab (anti-CTLA-4) was FDA-approved in 2011 for melanoma (61), and this was rapidly followed by the development of monoclonal antibodies targeting PD-1 (pembrolizumab and nivolumab) and PD-L1 (atezolizumab and durvalumab), which were approved in 2014 and 2019 respectively (61, 62).