Discovery of N-(1,2,4-Thiadiazol-5-yl)benzo[b]oxepine-4-carboxamide Derivatives as Novel Antiresistance Androgen Receptor Antagonists

Abstract

The ligand-binding pocket of the androgen receptor (AR) is the targeting site of all clinically used AR antagonists. However, various drug-resistant mutations emerged in the pocket. We previously reported a new targeting site at the dimer interface of AR (dimer interface pocket) and identified a novel antagonist M17-B15 that failed in oral administration. In this study, the head part of M17-B15 was substituted with divergent structures. Potent antagonist Z10 with benzo[b]oxepine was first identified. Subsequent structural optimization on the 2-oxopropyl moiety of Z10 generated the more powerful Y5 (IC₅₀ = 0.04 μM). Out of the ordinary, Y5 demonstrated dual mechanisms of action, antagonized AR by disrupting AR dimerization, and induced AR degradation via the ubiquitin-proteasome pathway. Furthermore, Y5 exhibited excellent activity against variant drug-resistant AR mutants comparable to recently approved darolutamide. Furthermore, Y5 effectively suppressed the tumor growth of the LNCaP xenograft via oral administration, providing a potential novel therapeutic for drug-resistant prostate cancer.