Abstract 5525: An Fc-competent bispecific antibody targeting PD-L1 and TIGIT induces strong immune responses and potent anti-tumor efficacy

Cancer Research(2022)

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Abstract Background: TIGIT (T-cell immunoglobulin and ITIM domain), which is primarily expressed on activated and 'exhausted' T and NK cells, is one of the most promising 'next generation' immune checkpoint target. Engagement of TIGIT to its ligands (i.e., PVR and PVRL2) leads to inhibitory signaling in T cells and promotes the functional exhaustion of tumor-infiltrating T lymphocytes. Anti-TIGIT monoclonal antibodies have shown clinical benefit when combined with anti-PD-L1 agents in NSCLC. Here, we describe our novel anti-PD-L1 × TIGIT bispecific antibody (PD-L1 × TIGIT biAb) that blocks both the PD-L1/PD-1 and TIGIT/PVR/PVRL2 pathways and has the potential to exhibit equal clinical benefit compared to current combination therapies. Methods: PD-L1 × TIGIT biAb was engineered with a fully-human IgG targeting TIGIT in a g1-Fc backbone, fused to a VHH at the C-terminus targeting PD-L1. Binding affinities and specificity testing were studied by flow cytometry and biolayer interferometry. The co-binding of the PD-L1 × TIGIT biAb to TIGIT and PD-L1 was detected by ELISA. The immunomodulatory functions of the PD-L1 × TIGIT biAb were evaluated using luciferase reporter cell assays and mixed lymphocyte reaction (MLR) assays in vitro, and human PBMC models in vivo. Results: The PD-L1 × TIGIT biAb binds with high affinity to the extracellular domain of human TIGIT and PD-L1 and can bind to TIGIT and PD-L1 simultaneously. In a competition assay, the PD-L1 × TIGIT biAb efficiently blocked the interaction between TIGIT and PVR/PVRRL2, and likewise PD-L1 to PD-1. The PD-L1 × TIGIT biAb induced higher luciferase signals than the anti-TIGIT or anti-PD-L1 mAbs alone in a luciferase reporter-based cell system and enhanced IFN-γ production in an MLR assay. In vivo, the PD-L1 × TIGIT biAb demonstrates similar anti-tumor efficacy to the combination of anti-TIGIT and anti-PD-L1 mAbs, which is stronger than the single-agents alone. We have also completed GLP-toxicity studies that have shown excellent safety. Conclusion: We have discovered a novel PD-L1 × TIGIT biAb, which induces strong immune responses in vitro and in vivo, supporting its clinical development for the treatment of human cancers. Clinical trials shall be initiating in early 2022. Citation Format: Shuang Dai, Weifeng Huang, Zhijun Yuan, Shaogang Peng, Jiayi Si, Chao Wang, Yao Yan, Xiaoniu Miao, Yingda Xu, Joanne Sun, Xiaolin Liu, Andy Tsun, Tianhang Zhai. An Fc-competent bispecific antibody targeting PD-L1 and TIGIT induces strong immune responses and potent anti-tumor efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5525.
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antibody,strong immune responses,immune responses,fc-competent,anti-tumor
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