Abstract 4844: A novel anti-TIGIT antibody (YH29143) enhances T cell activity and suppresses Treg cell activity and synergizes with anti-PD-L1 antibody

Abstract

Abstract TIGIT (T cell immunoreceptor with Ig and ITIM domains) is a T cell coinhibitory receptor, highly expressed on regulatory and memory CD4+, CD8+ T cells and natural killer (NK) cells. TIGIT binding of PVR (poliovirus receptor) on the surface of antigen presenting cells leads to downregulation of CD8+ T cell and NK cell responses in tumors. In this study, we sought to determine the efficacy of TIGIT blockade in antitumor immunity and demonstrate the synergistic effect of treatment with other checkpoint blockade such as anti-PD-L1. We generated anti-TIGIT monoclonal antibody that binds TIGIT with high affinity and blocks ligand binding. Anti-TIGIT antibody YH29143 was shown to increase T cell activities and suppress Treg cell activities from in vitro cell-based assays. We determined the crystal structure of YH29143 Fab fragment in complex with TIGIT and identified its epitope that overlaps with the PVR-binding interface. We also studied in vivo efficacy of YH29143 whether to inhibit the growth of tumor in two syngeneic colon tumor-bearing mouse models (CT26 and MC38). YH29143 reduced growth of both tumors compared to that of control IgG. In addition to these results, YH29143 showed synergistic efficacy for inhibition of tumor growth in combination with anti-PD-L1 antibody. From these tumor tissues, the ratio of CD8+ T cells to Treg cells was increased by treatment of anti-TIGIT antibody. Taken together, we evaluated the efficacy of YH29143, a potent anti-TIGIT monoclonal antibody, which enhanced T cell activation and suppressd Treg cell function in vitro, and efficiently inhibited tumor growth in vivo having synergistic effect with anti-PD-L1 antibody. These data also provide the rationale for YH29143 as a potential combination candidate for cancer immunotherapy with other immune checkpoint blockades. Citation Format: Kwang-Hoon Lee. A novel anti-TIGIT antibody (YH29143) enhances T cell activity and suppresses Treg cell activity and synergizes with anti-PD-L1 antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4844.