PDCD1 and neoplasm: These therapies, including cytotoxic T-lymphocyte antigen-4 (CTLA-4) inhibitors (e.g., ipilimumab) and programmed cell death-1 (PD-1) inhibitors (e.g., nivolumab and pembrolizumab), leverage the host immune system to target and kill tumour cells [1,2,3,4,5,6].