Abstract 3095: The development of CPI as a novel, next-generation DNA-targeting payload for ADCs

DNA targeting drugs represent one of cornerstones of anti-cancer therapy for both hematologic and solid tumor indications. Low potency anti-DNA compounds (e.g. platins, anthracyclines) are included in many standard-of-care (SOC) regimens, however their modest activity and overall toxicity profiles limit their therapeutic potential. To increase the therapeutic windowfor DNA-damaging agents, high potency anti-DNA compounds with enhanced anti-tumor activity have been delivered to tumors as payloadsof targeting modalities such as antibody-drug conjugates(ADCs). Herein, we describe the development of a novel DNA-damaging compound comprised of a dimeric structure of cyclopropylpyrrolo[e]indolones (CPIs) that was designed to alkylate DNA and generate toxic interstrand crosslinks (ICLs). In response to the CPI-induced formation of ICLs, CPI treatment of cells primarily activates the Fancomia anemia DNA damage response pathway, whereas other successful DNA-damaging ADC payloadssuch as calicheamicinactivate double-strand break response pathways. CPI shows ~860-fold greater potency than calicheamicinin a panel of cell lines derived from a broad spectrum of tumor indications. Importantly, this new CPI payloadretains potent activity in calicheamicin- and SOC-resistant tumor models (including overcoming overexpression of drug efflux pumps). When evaluated as payloadson anti- CD33targeting ADCs, the CPI conjugate showed dramatically improved efficacy over the corresponding calicheamicinconjugates in MDR+ tumor models. As a site-specific conjugate, the CPI ADC shows enhanced in vivo stability and possesses a wider therapeutic windowthan the corresponding conventional calicheamicinconjugate and other leading DNA-damaging conjugates on the CD33platform. Citation Format: Jennifer Kahler, Maureen Dougher, Jane Xu, Matthew Doroski, Andreas Maderna, Russell Dushin, Stephane Thibault, Mauricio Leal, Madan Katragadda, Christopher J. O9Donnell, Matthew Sung, Puja Sapra. The development of CPI as a novel, next-generation DNA-targeting payloadfor ADCs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3095. doi:10.1158/1538-7445.AM2017-3095