Abstract 5450: JSKN022, a first in class multi-specific ADC targeting PD-L1 and ITGB6/8 with an innovative DNA topoisomerase I inhibitor demonstrates encouraging efficacy in preclinical models

Background: Monoclonal antibodies targeting PD-1/PD-L1 have significantly transformed cancer therapy. However, the majority of patients still cannot get benefit from this treatment or may develop resistance afterwards. The increased expression of PD-L1 in tumors makes it an attractive target for ADC development leading to the most advanced program in registration trials. We developed a multi-specific ADC targeting another set of antigens, ITGB6/8. Integrins are cell surface receptors that usually mediate cell to cell adhesion. Integrin β6/8(ITGB6/8), which can only form a heterodimer with the αv integrin subunit, is highly expressed in various tumors. Utilizing our proprietary site-specific glycan conjugation, we generated JSKN022, an innovative PD-L1/ITGB6/8 targeting ADC, which structurally composed of a sdAb (single domain antibody) Fc fusion protein targeting PD-L1 and ITGB6/8, a cleavable linker and a novel DNA topoisomerase I inhibitor (T01, Alphatecan). In this study, the pharmacological activity of JSKN022 was evaluated using preclinical in vitro and in vivo models. Methods: Based on Envafolimab, we designed a novel sdAb-Fc fusion protein which targeting both PD-L1 and ITGB6/8. Then T01 was homogeneously and stably conjugated to glycan located on Fc. The conjugated product (DAR4) was thoroughly characterized by LC-MS. The binding specificity of JSKN022 and its internalization rate were assessed. Pattern of payload released were analyzed using LC-HRMS. Serum stability was tested across various species. In vitro cell growth inhibition and in vivo antitumor efficacy of JSKN022 were examined using a range of cancer cell lines and CDX models with parental antibody ADC as control. Results: JSKN022 demonstrated specific binding to the αvβ6/8 protein, without cross-reactivity with other members of integrin family. JSKN022 exhibited a consistent DAR4. Bridging ELISA indicated that JSKN022 can simultaneously bind to both PD-L1 and ITGB6/8. Flow cytometry binding assays revealed that JSKN022 possessed a superior binding capacity compared to both parental antibodies. Correspondingly, the naked antibody of JSKN022 showed an increased internalization rate relative to parental antibodies in HCC4006 and BxPC-3 tumor cells. JSKN022 effectively inhibits the proliferation of antigen-positive cancer cells and exhibited enhanced tumor suppression compared to the single-target ADCs. Furthermore, benefiting from glycan conjugation, JSKN022 demonstrated excellent stability in serum from rats, mice, monkeys, and humans, with minimal T01 release. Conclusion: This preclinical study suggests JSKN022, as a first in class multi-specific PD-L1/ITGB6/8 ADC, might potentially bring in novelty in the therapeutic approach for cancers that are refractory or resistant to PD-1/PD-L1 inhibitors. Citation Format: Ting Xu, Ling Wang, Yongli Dong, Chuankun Shan. JSKN022, a first in class multi-specific ADC targeting PD-L1 and ITGB6/8 with an innovative DNA topoisomerase I inhibitor demonstrates encouraging efficacy in preclinical models [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 5450.