Targeting PD-L1Glycosylation with Site-Specific Aptamersfor Enhanced Immune Checkpoint Blockade

Abstract Programmed death-ligand 1 (PD-L1) critically relies on extensive N-glycosylation at four conserved sites to regulate its immune-checkpoint function. However, the distinct roles of individual glycans remain poorly understood because of a lack of site-specific tools, which also limits the efficacy of current PD-1/PD-L1 blockade therapies. Here, we developed a glycoprotein-targeted Systematic Evolution of Ligands by EXponential enrichment platform (Glyco-SELEX) using an indole-incorporated DNA library to screen aptamers against epitope-specific glycans. Using natively glycosylated PD-L1 isolated from cell membranes as the selection target, we identified a panel of aptamers that can discriminate glycosylation sites on PD-L1. Our results demonstrated that aptamers targeting glycans at the N35 or N192 site effectively disrupt the PD-1/PD-L1 interaction. Moreover, by engineering a bivalent aptamer directed against both sites, the antitumor activity of CAR-T cells was significantly enhanced. This work not only resolves the functional ambiguity of PD-L1 glycosylation but also establishes a versatile platform for developing therapeutics against epitope-specific glycans.