27 Cancer cells escape apoptosis via this interaction of PD-1 and CTLA-4 with T-cells but monoclonal antibodies to these molecules can induce tumour cell death. PD-1 inhibitor, nivolumab, and CTLA-4 inhibitor, ipilimumab, have been tested in combination with one another resulting in longer PFS in melanoma patients, however, caused a greater proportion of adverse events. 27,28 Anti-PD-1 is safe to administer to patients, even with cardiac, hepatic and renal dysfunction. 29,30. This evidence concerns the gene CTLA4 and cancer.