CD274 and neoplasm: However, antibodies have disadvantages such as high production cost, poor oral bioavailability and low tumor penetration, so the development of non-antibody PD-1 inhibitors has become a research hotspot in recent years, including peptide inhibitors [53], non-peptide small molecule inhibitors [54, 55], nucleic acid drugs [56], etc. These drugs have shown promising efficacy and are expected to expand the pathway of blocking PD-1/PD-L1 [57].