Abstract 2124: Validation of the intelligent glycotransferase-dependent conjugation (iGDC) platform: A groundbreaking approach for next-generation HER2-targeting ADC GQ1012 with enhanced druggability, potency, and safety

Abstract

Abstract Background: Antibody glycan remodeling has emerged as a promising site-specific conjugation technology to develop ADCs, while most reported cases suffer from complicated CMC process and scalability challenges. We report herein an innovative, streamlined one-enzyme, one-step glycan remodeling technology, i.e. intelligent Glycotransferase-Dependent Conjugation (iGDC), that enables the site-specific conjugation of various biologic modalities including monoclonal antibody, bispecific antibody and Fc fusion proteins. Employing immobilized enzymes and a continuous-flow process, iGDC efficiently tethers payloads to the N-297 glycan site without requiring antibody engineering. In contrast to alternative conjugation techniques, iGDC offers superior versatility, product quality, process efficiency, scalability, and cost-effectiveness. Validation of the iGDC platform is exemplified by GQ1012, a HER2-targeting ADC featuring the potent Topoisomerase I inhibitor, TopoIx. Preclinical studies demonstrated GQ1012's outstanding anti-tumor efficacy in diverse in vitro and in vivo models, displaying robust synergistic effects with anti-PD-1 therapy and excellent tolerability in pre-tox studies involving monkeys with no signs of lung diseases, surpassing those of Enhertu. Results: GQ1012, developed through iGDC, utilized a highly hydrophilic, stable branch linker to conjugate TopoIx to an anti-HER2 antibody, achieving high conjugation efficiency confirmed by DAR analysis. The ADC maintained comparable antigen binding affinity and internalization compared to the parental antibody, exhibiting potent cytotoxicity against HER2-positive cancer cells. Despite glycan remodeling with iGDC leading to the removal of ADCC function, GQ1012 demonstrated no off-target cytotoxicity in HER2-negative cells and displayed a robust bystander killing ability in co-culture assays. In various in vivo models, GQ1012 demonstrated similar or superior antitumor efficacy compared to Enhertu, showcasing strong synergy with anti-PD-1 therapy. Stability studies confirmed GQ1012 maintains a highly stable linker, minimizing DAR reduction. Preliminary toxicity studies in monkeys following repeated intravenous infusions of GQ1012 showcased excellent safety and pharmacokinetics at specified doses and the potential for an extended therapeutic window compared to Enhertu. Conclusion: The validation of the iGDC platform through GQ1012 highlights its adaptability and efficiency in producing highly homogeneous next-generation ADCs without requiring antibody engineering. GQ1012 presents promising potential as a next generation HER2 ADC with an expanded therapeutic window compared to Enhertu, supported by extensive in vitro, in vivo assessments, and preliminary toxicity studies. Citation Format: Meijun Xiong, Zengyan Mu, Meiling Xu, Chong Liu, Bo Dai, Junhao Wang, Xinju Gao, Lili Shi, Paul H. Song, Gang Qin. Validation of the intelligent glycotransferase-dependent conjugation (iGDC) platform: A groundbreaking approach for next-generation HER2-targeting ADC GQ1012 with enhanced druggability, potency, and safety [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2124.