Abstract 7277: Discovery of INV-9956, an orally available and highly selective Cyp11A1 inhibitor for the treatment of castration-resistant prostate cancer with drug resistant AR mutations

Abstract

Abstract Androgen Receptor (AR) signaling plays a profound role in prostate cancer and development. Efforts in harnessing androgen and AR axis for castration-resistant prostate cancer treatment have led to discovery of several therapeutics, including AR antagonists and Cyp17 inhibitors. However, resistance to these approved therapeutics has emerged, and remained a significant unmet medical need. Among the prominent resistance mechanisms of action are restored androgen signaling via AR amplification and overexpression, and gain-of-function mutations occurring at AR ligand binding domain that can be agonized by existing AR antagonists and/or non-androgenic steroids such as glucocorticoids. Targeting Cyp11A1 that catalyzes the formation of pregnenolone is effective to ablate biosynthesis of androgens and all steroids and thus holds promise to deliver coverage of a significant percentage of drug resistant AR mutations and benefit CRPC patients post treatment with AR antagonists or Cyp17 inhibitors. Here we present discovery and characterization of INV-9956, an orally available, selective, and potent Cyp11A1 inhibitor with well-acceptable pharmacokinetic properties. INV-9956 potently inhibits biosynthesis of pregnenolone and other androgens in H295R cells with IC50 at single-digit nanomolar, suppresses proliferation of prostate cancer cell lines harboring major clinically acquired drug resistant AR LBD mutations, such as AR L702H using coculture assays. Orally administered INV-9956 showed consistent dose dependent PK/PD correlations across animal species. Particularly, INV-9956 displayed pronounced tumor inhibition superior to known competitors in a CRPC VCaP xenograft model and in a “humanized” animal model. Furthermore, INV-9956 displayed a good tox profile in 14-day repeated dosing rat and dog studies, supported by a high selectivity to Cyp11A1 over other Cyp family members, clean hERG and mini-Ames, and no significant off-target activity in a safety panel screen. The promising preclinical profiles of INV-9956 lend strong support to its potentials in addressing unmet needs in CRPC treatments and warrant clinical development. Citation Format: Chang Bai, Danqi Chen, Zilei Xia, Shujuan Huang, LIshan Lin, Zhaopie Zeng, Jing Su, Yongkui Sun. Discovery of INV-9956, an orally available and highly selective Cyp11A1 inhibitor for the treatment of castration-resistant prostate cancer with drug resistant AR mutations [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 7277.