CTLA4 and neoplasm: Agents such as nivolumab/pembrolizumab targeting programmed cell death protein 1 (PD-1) or ipilimumab targeting cytotoxic T-lymphocyte -associated protein 4 (CTLA-4) activate T cells by inhibiting the interaction of T cell surface proteins (PD-1/CTLA-4) with their respective ligands on antigen presenting cells and tumor cells (5, 6).