Abstract 2656: Reversible chemical modification of antibodies: A complementary approach to tuning FcγR binding that maintains anti-tumor activity while mitigating peripheral immune activation

Abstract Modification of effector function has proven to be an effective modality for optimizing activity and tolerability of therapeutic antibodies. Currently available methods to modulate effector function include the introduction of point mutations in the Fc region and glycan engineering of the antibody. Here we present an alternative and complementary method of tuning effector function utilizing a conjugation-based approach. This methodology uses conjugation of polyethylene glycol (PEG) to native cysteines of an antibody to impair FcγR binding of antibodies to innate immune effector cells. Utilizing maleimide or disulfide conjugation techniques, attenuated effector function can be either permanent or restored over time through a de-conjugation process. Impacts of PEGylation on FcγR binding, signaling, and restoration of function were assessed in vitro and in vivo. As a proof-of-concept, the lead technology was applied to an agonist CD40 antibody, which resulted in significant reductions in systemic cytokine production in hCD40 mice and non-human primates, while demonstrating retained efficacy and improved pharmacokinetics. Additionally, we combined the conjugation technology with glycan engineering and FcγR enhancing point mutations to impart unique effector function profiles to clinical antibodies. This simple, modular approach can be rapidly applied to existing antibodies to reduce immune-driven toxicities, such as infusion reactions, and optimize effector function activity. Citation Format: Philip N. Moquist, Chris I. Leiske, Noah A. Bindman, Xinqun Zhang, Nicole Duncan, Weiping Zeng, Serena W. Wo, Abbie Wong, Clark M. Henderson, Karalyne Crowder, Haley D. Neff-LaFord, Django Sussman, Shyra J. Gardai, Matthew R. Levengood. Reversible chemical modification of antibodies: A complementary approach to tuning FcγR binding that maintains anti-tumor activity while mitigating peripheral immune activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2656.