Abstract 5558: Discovery of a novel Claudin 6 X 4-1BB bispecific antibody with potent anti-tumor activity through conditional 4-1BB activation

Abstract

Abstract Background Claudin 6 (CLDN6) is a tight junction transmembrane protein normally only expressed during embryonic development, but is aberrantly expressed in a variety of tumors, including ovarian cancer, testicular cancer, hepatocellular and lung adenocarcinoma. Here, we generated a CLDN6 X 4-1BB bispecific antibody (BsAb) which could conditionally activate T cells through 4-1BB stimulation upon CLDN6 engagement, positioning it as a potential novel immunotherapy for ovarian cancer and other CLDN6 positive tumors. Methods CLDN6 X 4-1BB BsAb was evaluated for its antigen binding through cell-based binding assay. In vitro function of the antibody was confirmed in a 4-1BB signaling reporter assay and primary human PBMC assay. In vivo efficacy of the antibody was further demonstrated in 4-1BB humanized syngeneic mouse model. Ex vivo analysis of tumor infiltrating and peripheral immune cells was conducted by FACS. Safety parameters such as liver enzymes and pathology upon antibody administration were also assessed. Results CLDN6 X 4-1BB BsAb showed strong binding to several ovarian cancer cell lines with different levels of CLDN6 expression. Functional evaluation of CLDN6X4-1BB BsAb indicated that the activation of 4-1BB signaling was dependent on CLDN6 expression on tumor cells and the activity was stronger than reference 4-1BB monoclonal antibody urelumab. In a humanized 4-1BB mouse model, CLDN6X4-1BB BsAb showed tumor growth inhibition superior to the combination of anti-CLDN6 and anti-4-1BB monospecific antibodies, and the treatment effect was associated with an increase in tumor infiltrating CD45 and CD8 cells as well as CD8/Treg ratio. From the safety perspective, there were no significant changes in liver enzymes or liver histopathology following repeated BsAb administration, suggesting little risks for liver toxicity commonly induced by other 4-1BB agonist antibodies. Conclusions We have successfully generated a novel CLDN6-targeted 4-1BB bispecific antibody which could induce potent 4-1BB stimulation and anti-tumor activity in a CLDN6-dependent manner while minimizing the risk of liver toxicity. Taken together, these data support further development of CLDN6 X 4-1BB bispecific antibody towards IND and clinical trial in 2022. Citation Format: Jian Li, Wenqing Jiang, Yan Liu, Zhengyi Wang, Xi Chen, Taylor B. Guo. Discovery of a novel Claudin 6 X 4-1BB bispecific antibody with potent anti-tumor activity through conditional 4-1BB activation [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 5558.