Abstract 5733: Development of a topoisomerase 1 inhibitor platform technology for efficacious and well tolerated ADCs

Abstract Topoisomerase 1 (TOP1) inhibitors are a class of cytotoxic small molecules that have demonstrated effectiveness as therapeutic agents in cancer. However, the broad clinical application has been hindered by poor pharmacokinetic profiles and off-target toxicities. Antibody-drug conjugates (ADCs) enable the targeted delivery of cytotoxic payloads by specifically targeting cell-surface antigens expressed on cancers reducing systemic exposure and toxicity. TOP1-ADCs have received FDA approval for HER2- (trastuzumab-deruxtecan) and Trop2- (sacituzumab-govitecan) expressing solid tumors, demonstrating the promise for this drug class to improve the lives of patients. We have developed a novel drug-linker using a potent TOP1 inhibitor with desirable ADME properties, and a hydrophilic glycoside linker as a platform technology enabling ADCs with favorable physicochemical and biological properties. The TOP1 inhibitor payload was optimized for potency, with reduced P-glycoprotein efflux and enhanced permeability. The hydrophilicity of the linker facilitates the development of highly loaded ADCs (8 drugs/mAb) with high plasma stability, low aggregation, and pharmacokinetics similar to parental antibody. The resultant ADCs are potent and immunologically specific with activity in multidrug-resistant tumor models and bystander activity in heterogenous antigen models. Human cancer cell derived xenograft models demonstrated potent and specific ADC anti-tumor activity with several targets and indications. Improved activity was observed compared to corresponding govitecan- and deruxtecan-based ADCs. ADCs prepared from this drug-linker technology were well tolerated in rats after repeat administration of 60 mg/kg every 4 days for 4 doses. The excellent anti-tumor activity in several models and favorable safety profile demonstrates this platform TOP1 drug-linker technology has the potential for development as ADCs against many cancer targets. Citation Format: Ryan Lyski, Lauren Bou, Johann Sigurjonsson, David Meyer, Calvin Neace, David Ortiz, Katie Snead, Kaleb Smith, Steven Jin, Nicole Stevens, Julia Cochran, Kaveh Alizadeh, Narayana Yeddula, Erica McKinney, Adam Peterson, Lindsay Dotloe, Jessica Simmons, Christopher Carosino, Kim Emmerton, Nancy Everds, Scott Jeffrey, Peter Senter. Development of a topoisomerase 1 inhibitor platform technology for efficacious and well tolerated ADCs [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 5733.