N-glycosylation of PD-1 promotes binding of camrelizumab

PD-1 is a highly glycosylated inhibitory receptor expressed mainly on T cells. Targeting ofPD-1 with monoclonal antibodies (MAbs) to block the interaction with its ligandPD-L1 has been successful for the treatment of multiple tumors. However, polymorphisms at N-glycosylation sites ofPD-1 exist in the human population that might affect antibody binding, and dysregulated glycosylation has been observed in the tumor microenvironment. Here, we demonstrate varied N-glycan composition inPD-1, and show that the binding affinity of camrelizumab, a recently approvedPD-1-specificMAb, to non-glycosylatedPD-1 proteins fromE. coliis substantially decreased compared with glycosylatedPD-1. The structure of the camrelizumab/PD-1 complex reveals that camrelizumab mainly utilizes its heavy chain to bind toPD-1, while the light chain sterically inhibits the binding ofPD-L1 toPD-1. Glycosylation of asparagine 58 (N58) promotes the interaction with camrelizumab, while the efficiency of camrelizumab to inhibit the binding ofPD-L1 is substantially reduced for glycosylation-deficientPD-1. These results increase our understanding of how glycosylation affects the activity ofPD-1-specificMAbs during immune checkpoint therapy.