The FG Loop of PD-1 Serves as a 'Hotspot' for Therapeutic Monoclonal Antibodies in Tumor Immune Checkpoint Therapy

Summary Programmed cell death 1 (PD-1)/PD-1 ligand-1 (PD-L1)-blocking monoclonal antibodies (mAbs) have taken center stage for tumor immune checkpoint therapy. Identification of the “hotspots” on PD-1 for mAbs will help to develop next-generation oral deliverable agents with long-lasting efficacy. Here, we identified two PD-1-targeting mAbs, GY-5 and GY-14, with PD-1/PD-L1-blocking efficacy. Complex structural information revealed that both mAbs mainly bind to the FG loop of PD-1, which also contributes multiple interactions with PD-L1. The FG loop adopts substantially varied conformations upon binding to different mAbs, providing a novel targetable region for the development of PD-1-specific biologics and small chemical molecules. Glycosylation modifications of PD-1 could be observed in three of the four potential N-linked glycosylation sites. However, the binding of GY-5 and GY-14 to PD-1 was not affected by glycosylation. These findings broaden our understanding of the mechanism of anti-PD-1 mAbs and provide insight into the development of agents targeting PD-1.
Graphical Abstract
Highlights • GY-5 and GY-14 show efficient anti-tumor efficacy in NCG mouse model • Both GY-5 and GY-14 bind to the FG loop of PD-1 • Glycosylation is observed in PD-1, but not involved in binding to GY-5 and GY-14 • The loops of PD-1 may serve as “hotspot” for development of PD-1-targeting biologics
Biological Sciences; Immunobiological Therapy Center; Structural Biology