Abstract 4805: Dual-target CAR-T strategy for MSLN and CLDN18.2: Advancing cancer treatment with superior efficacy and safety

Abstract Background: CAR-T-cell therapy has achieved great success in the treatment of hematological malignancies. However, due to the characteristics of solid malignant tumors, CAR-T for solid tumors is still in the exploration stage. The restricted expression of MSLN and CLDN18.2 in normal tissues, combined with their abnormal overexpression in various tumor tissues, makes them highly promising targets for CAR-T therapy. Although targeting CLDN18.2 demonstrates significant therapeutic potential, its application in CAR-T therapy carries the risk of gastrointestinal (GI) toxicities, due to on-target/off-tumor adverse effects. MSLN and CLDN18.2 are not co-expressed in normal human tissues but are simultaneously overexpressed in various tumor tissues, including gastric and pancreatic cancers, both with limited treatment options and poor prognoses. Methods: Considering that CLDN18.2-BBZ exhibited gastrorrhagia toxicity in our preclinical mouse models, we designed OriC613 using “AND” logic gate, aiming to improve safety while maintain anti-tumor efficacy. OriC613 employing an anti-CLDN18.2 scFv with high binding activity and an anti-MSLN VHH with moderate binding affinity, eliciting completely activation only targeting MSLN&CLDN18.2 double positive tumor cells. Results: OriC613 exhibits more potent in vitro/vivo cytotoxicity efficacy against MSLN&CLDN18.2 double positive cells than MSLN-CD3Z, and IFN-γ and IL-2 released by OriC613 were positively dependent on MSLN and CLDN18.2 expression levels. Notably, OriC613 demonstrated no cytotoxicity towards cells expressing CLDN18.2 alone, both in vitro and in vivo, indicating mitigate the toxicity toward CLDN18.2 positive normal stomach cells. OriC613 exhibited efficacy, prolonged survival and no GI toxicities in tumor stress model (NUGC-4 cells, MSLNlowCLDN18.2med), even when targeting relatively large (976 mm3) tumor sizes, indicating its potential effectiveness in patients with high tumor burden. OriC613 showed efficacy, re-enhanced production of IFN-γ and T cell expansion in a tumor re-stress model for pancreatic cancer (AsPC-1-hCLDN18.2 cells, MSLNlowCLDN18.2high), with T cells homing to bone marrow and spleen (at Day 115, endpoint). These findings demonstrate that OriC613 enhance both the safety and the effectiveness and persistence of its anti-tumor activity. Conclusions: The impressive antitumor effects and promising safety of OriC613 highlight the need for continued clinical trials in pancreatic and gastric cancer patients. Citation Format: Shasha Yang, Kai Wu, Zhongjun Shi, Jiantao Wang, Xuefeng Kong, Huajing Wang, Xiaowen He. Dual-target CAR-T strategy for MSLN and CLDN18.2: Advancing cancer treatment with superior efficacy and safety [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4805.