Immune checkpoint inhibitors (ICIs), such as anti-programmed cell death 1 (PD-1) and anti-PD-ligand1 (PD-L1) antibodies, have been approved for the treatment of various tumour types in humans, including malignant melanoma, non-small cell lung cancer (NSCLC), and renal cell cancer [7–10]. The gene discussed is PDCD1; the disease is neoplasm.