Abstract A085: Engineered novel bioactive Nectin-4 dimer protein significantly enhances the binding of TIGIT

Abstract The goals of this study are to: (a) create a novel soluble bioactive Nectin-4 dimer molecule mimicking its native dimer quaternary structure on the cell surface and (b) evaluate the recombinant Nectin-4 dimer binding potency to its receptor vs the monomer form, so that the dimer can be used as an immunogen and an antigen to increase the potential of cancer therapeutic antibody and vaccine discovery when targeting quaternary structural epitopes. Nectin-4 is a cell adhesion molecule belonging to the nectin family. It's involved in cell-cell junctions and plays a role in cancer progression by influencing cell adhesion, migration, and proliferation. Nectin-4 is overexpressed on various types of tumor cells including breast, lung, ovarian and pancreatic cancers. Nectin-4 has been recently identified as a novel ligand of T cell immunoglobulin and ITIM domain (TIGIT) and interaction between Nectin-4 and TIGIT inhibits NK cell cytotoxicity thus suppressing immune responses, allowing cancer cells to evade immune surveillance. Nectin-4 and Nectin-1 interact in a heterophilic manner, however in the context of cancer, altered expression of Nectin-4 and Nectin-1 can contribute to tumor progression. Nectin-4 is a type 1 single transmembrane protein, and can form homodimers on the cell surface. While therapeutics such as Enfortumab Vedotin, an antibody-drug conjugate, binds Nectin-4 on the surface of cancer cells, mimicking the Nectin-4 dimer quaternary structure can present many more critical opportunities for therapeutic antibody and vaccine discovery. To better mimic the native dimer conformation and quaternary structure, we designed a novel soluble Nectin-4 dimer with 3 extracellular domains fused to a dimer motif at the C-terminus. The Nectin-4 dimer protein was expressed and purified from HEK293 cells and confirmed by SDS-PAGE and Western blot analyses. We characterized the Nectin-4 dimer protein binding potency to TIGIT and Nectin-1 by ELISA. Very interestingly, the results demonstrated that the Nectin-4 dimer binding potency to TIGIT increased dramatically as measured by ELISA, compared to the Nectin-4 monomer protein. Conversely, the Nectin-4 dimer binding to Nectin-1 monomer was significantly decreased, compared to Nectin-4 monomer, as expected. We also studied Nectin-4 dimer immunogenicity using a Nectin-4 dimer DNA immunization to induce potent antibody responses in mice. In summary, these findings imply that the Nectin-4 dimer protein is bioactive and in the desirable conformation, resulting in an increased binding potency to its receptor TIGIT, reduced binding to Nectin-1 (as expected), and eliciting strong antibody responses in mice. This novel Nectin-4 dimer protein can be a very useful molecule for cancer research, therapeutic antibody and vaccine discovery. The Nectin-4 dimer protein can be used to: (i) elicit antibody responses against the dimer quaternary structure, (ii) screen antibodies targeting more conformational epitopes, and (iii) study the Nectin-4 and TIGIT ligand/receptor interactions. Citation Format: Christofer Walsh, Timothy Smith, Mikhail Rashkovskii, Richard Parent, Jean Qiu, Shixia Wang. Engineered novel bioactive Nectin-4 dimer protein significantly enhances the binding of TIGIT [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A085.