Abstract 6527: Targeting glycosylated PD-1 induces potent anti-tumor immunity

Immunotherapy targeting programmed cell death protein 1 (PD-1) and programmed cell death 1 ligand 1 (PD-L1) immune checkpoints represents a major breakthrough in cancer treatment. PD-1 is an inhibitory receptor expressed on the surface of activated T cells that dampens T-cell receptor (TCR)/CD28 signaling by engaging with its ligand PD-L1 expressed on cancer cells. Despite the clinical success of PD-1 blockade using monoclonal antibodies, most patients do not show promising results, and the underlying regulatory mechanisms of PD-1 remain incompletely defined. Here, we showed that PD-1 is extensively N-glycosylated in T cells, and the intensities of its specific glycoforms are altered upon TCR activation. Glycosylation is critical for maintaining PD-1 protein stability and cell surface localization. Importantly, the glycosylation of PD-1, especially at the N58 site, is essential for mediating the interaction with PD-L1. A monoclonal antibody that specifically targets glycosylated PD-1, STM418, exhibits higher binding affinity to PD-1 than FDA-approved PD-1 antibodies, potently inhibits PD-L1/PD-1 binding, and enhances anti-tumor immunity. Our findings provide novel insights into the functional significance of PD-1 glycosylation and offer a rationale for targeting glycosylated PD-1 as a potential strategy for immunotherapy. Citation Format: Yuhan Wang, Linlin Sun, Riyao Yang, Jielin Liu, Yufan Qiu, Jennifer L. Hsu, Jong-ho Cha, Li-Chuan Chan, Jung-Mao Hsu, Heng-Huan Lee, Yun-Ju Lai, Kay-Hooi Khoo, Ezra M Chung, Chia-Wei Li, Yong-Soo Kim, Andrew H Park, Yi Yang, Stephen S. Yoo, Mien-Chie Hung. Targeting glycosylated PD-1 induces potent anti-tumor immunity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6527.