Multiple preclinical studies have showed that the PD-1 axis in the tumor causes the resistance to immune-mediated cytolysis, while blocking PD-L1 or PD-1 with specific mAbs in tumors could reverse tumors’ inherent resistance to cytotoxicity by T cells.381–384 However, solely blocking PD-L2 did not demonstrate any antitumor effect.385 Following the success of preclinical studies, mAbs targeting the PD-1 axis were designed and showed remarkable efficacy in clinical trials. The gene discussed is PDCD1; the disease is neoplasm.