PD-L1 peptides in cancer immunoimaging and immunotherapy

The interaction between programmed death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) constitutes a critical immune checkpoint pathway that leads to immune tolerance in cancer cells and impacts antitumor treatment. Monoclonal antibody blockade of the PD-L1 immunoinhibitory pathway has demonstrated significant and lasting clinical antitumor responses. Furthermore, PD-L1 serves as an important biomarker for predicting the effectiveness of immune checkpoint inhibitors (ICIs). To date, numerous studies based on monoclonal antibodies have been carried out to detect the expression levels of PD-L1 and predict the antitumor effectiveness of PD-L1 ICIs. However, due to the deficiencies of monoclonal antibodies, researches of PD-L1 peptides have received increasing attention. PD-L1 peptides present promising candidates due to their advantages, including reduced manufacturing costs, enhanced stability, decreased immunogenicity, faster clearance and improved tumor or organ penetration, thereby offering broad application prospects in cancer immunoimaging and immunotherapy. In this review, we analyze the existing evidence on PD-L1 peptides in cancer immunoimaging and immunotherapy. First, the design techniques of different types of PD-L1 targeting peptides and their strengths and weaknesses are briefly introduced. Second, the recent advancements in immunoimaging and the development trends in immunotherapy are summarized. Finally, the existing challenges and future directions in this field are comprehensively deliberated.