CTLA4 and metastatic melanoma: Monoclonal antibodies, such as Ipilimumab targeting cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) (Hodi et al., 2010), Atezolizumab targeting programmed death 1 (PD-1) receptor (Krishnamurthy and Jimeno, 2017), have been approved by FDA as immune checkpoint blocker for the treatments of metastatic melanoma and metastatic urothelial carcinoma or non-small-cell lung cancer, respectively.