Blocking the PD-1/PD-L1 axis (programmed cell death proteins 1/programmed cell death proteins ligand 1) through immunotherapy, represented by the administration of ICK inhibitors (ICIs), has demonstrated great efficacy in the immunotherapeutic treatment of malignant melanoma, lung carcinoma, renal cancer, and gastric cancer, and remains the central way of targeting and activating the immune system. The gene discussed is PDCD1; the disease is gastric cancer.