In this type of therapy, the immune system is recruited to fight against tumor development and expansion, and the most successful immunotherapeutics to date have been immune checkpoint inhibitors, such as anti-programmed cell death protein 1 (PD-1), anti-PD-L1, and anti-CTLA-4 antibodies.1 Under normal conditions, T-cells can identify and kill tumor cells by recognizing the antigens on tumor cells. Here, PDCD1 is linked to neoplasm.