Abstract PO3-26-01: Preclinical in vitro and in vivo characterization of a novel, wild-type-sparing, PI3Kα H1047R mutant-selective inhibitor

Abstract The PI3K pathway is a key cell cycle regulating pathway that has an established role in tumor growth and development. Specifically, the H1047R and helical domain mutations E542K/E545K of the p110α subunit of PI3K are known activating mutations that are targeted by inhibitors under clinical investigation as well as by approved drugs. PI3Kα mutations are prevalent in patients with breast, colorectal, lung, endometrial, and numerous other cancers. The approved PI3Kα inhibitor, alpelisib, shows promise for this targeted class with improvements in progression-free survival in HR+/Her2- breast cancer in combination with fulvestrant. However, tolerability concerns such as hyperglycemia, gastrointestinal issues, and skin reactions have emerged related to on-target inhibition of wild type PI3Kα. These issues likely limit dose administration leading to exposure which is suboptimal for maximal efficacy and creates an opportunity to identify an inhibitor with an improved tolerability profile that targets oncogenic mutations while sparing wild type PI3Kα. Herein, we present preclinical in vitro and in vivo activity of a novel, wild type sparing PI3Kα inhibitor which is potent against the oncogenic H1047R mutation. Citation Format: Aaron C. Smith, Ben Arwood-Levine, Alexandra Born, Richard Brizendine, Payal Chatterjee, Mark J. Chicarelli, Michael L. Conner, Brad Fell, Jennifer Fulton, Anna Guarnieri, Ravi Jalluri, Hailey Knox, Keith Koch, Daniel Krischlunas, Vijay Kumar, Colin McHugh, Brent Mclean, Kelsey Nassar, Brad Newhouse, Rob Rieger, John Robinson, Marelí Rodriguez, Leah Salituro, Lee Stunkard, Francis Sullivan, Roy Turton, Shannon Winski, Yeyun Zhou. Preclinical in vitro and in vivo characterization of a novel, wild-type-sparing, PI3Kα H1047R mutant-selective inhibitor abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-26-01.