LAUSR

The CD226 (DNAM-1) axis has emerged as an important immune-modulatory pathway that regulates T cell and NK cell effector functions in the solid tumor microenvironment. Three inhibitory receptors, TIGIT, CD96, and PVRIG, inhibit the activating receptor CD226 by competing for shared ligands (CD112 and CD155) expressed on tumor cells and myeloid cells. Blocking the TIGIT receptor with monoclonal antibodies is a major focus of current clinical development efforts. However, the effectiveness of targeting TIGIT alone in a clinical setting has yet to be demonstrated. We hypothesize that blocking TIGIT alone may not lead to an optimal clinical outcome since immuno-stimulatory interaction between the ligands CD112 and CD155 with CD226 can be competed by inhibitory receptors CD96 and PVRIG in addition to TIGIT. It is therefore interesting to investigate whether all these checkpoints play critical roles in the tumor environment and if inhibiting one or more may be necessary to achieve the maximum CD226 activation in both innate and adaptive immune cells. To address that, we have conducted single-cell analysis and demonstrated high expression levels and co-expression of the three inhibitory receptors on T cell subsets and NK cells in the tumor microenvironment for multiple tumor types. Thus, simultaneous blockade of two or more of these receptors might be required for full CD226 activation and T and NK cell-mediated anti-tumor immunity. We envision developing blocking antibodies to these receptors in the CD226 axis toward potential combinations or multi-specific antibody therapies against solid tumors. Antibodies against all three checkpoints, i.e., TIGIT, CD96, and PVRIG, were selected based on receptor binding and their ability to block the receptor interaction with their ligands. We have demonstrated the functionality of the antibodies against these three targets and explored the best approach to alleviate the suppressive regulation of CD226 signaling. Detailed characterizations of these antibodies have been performed, and multi-specific antibodies have been generated and evaluated. Through this effort, we aim to define and develop the best therapeutic strategy for unleashing the CD226 axis for T and NK cell-mediated anti-tumor immunity. Citation Format: Tom Li Stephen, Qian Zhang, Byung-Kwon Lee, Chao Kong, Rain Sun, Jia Wu, Jie Cui, Hillary Shah, Wenhua Xu, Yun-Yueh Lu, Joshua Whitener, Emily Jackson, Jinping Gan, Francisco Adrian, Liang Schweizer. Maximizing the outcome of CD226 stimulation through targeting beyond TIGIT signaling with combination and multi-specific approaches for cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3477.