Abstract B024: Leveraging synthetic lethality across EP300-mutant solid cancers through selective CBP degradation

Abstract

Abstract CREB binding protein (CBP) and E1A binding protein P300 (EP300) are paralog histone acetyltransferases that can function as transcriptional coactivators to regulate diverse cellular processes. Mutations in CBP and EP300 have been implicated in the biology of various cancer types. Functional genomic screens have revealed a bidirectional synthetic lethal relationship between these paralogs in tumor cells, highlighting a therapeutic opportunity in targeting CBP selectively in EP300-mutant cancers while sparing other tissues in which EP300 is intact. This strategy would enable an improved therapeutic window beyond those observed with dual CBP/EP300 inhibitors, which exhibit hematological toxicities. However, due to the high degree of homology between the CBP and EP300 proteins, identifying chemical matter that selectively disrupts CBP activity has proven challenging. Here, we demonstrate selective and potent CBP degrader compounds that disrupt proliferation in EP300-mutant cancer cell line models. Notably, these degraders have little impact on cell lines with intact EP300. Moreover, in cell line-derived xenograft (CDX) tumor models, we achieve potent and sustained CBP degradation and associated tumor growth inhibition. Our CBP-selective protein degraders have the potential to be a first-in-class therapeutic option for patients with tumors harboring EP300 mutations. Citation Format: Darshan Sappal, Ammar Adam, Hafiz Ahmad, Benjamin Adams, Ketaki Adhikari, Wesley Austin, Breanna Bullock, Julie Di Bernardo, Thomas Dixon, Danette Daniels, Claudi Dominici, GiNell Elliott, Brian Ethell, Anais Gervais, Md Imran Hossain, David Huang, David Lahr, Laura La Bonte, Mei Yun Lin, David Mayhew, Karolina Mizeracka, Solymar Negretti, Tyler Nguyen, Olga Prifti, Shawn Schiller, Brenna Sherbanee, David Terry, Nihan Ucisik, Elizabeth Wittenborn, Molly M Wilson, Qianhe Zhou, Mark Zimmerman. Leveraging synthetic lethality across EP300-mutant solid cancers through selective CBP degradation [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr B024.