PDCD1 and neoplasm: Ipilimumab targets cytotoxic T lymphocyte antigen 4 (CTLA-4) on T cells, while Nivolumab and Pembrolizumab target programmed cell death protein 1 (PD-1) on T cells, and Atezolizumab targets programmed cell death ligand 1 (PD-L1) on tumour cells and tumour-infiltrating immune cells [4].