Development of Novel AKR1C3 Inhibitors as New Potential Treatment for Castration-Resistant Prostate Cancer.

Aldo-keto reductase (AKR) 1C3 catalyzes the synthesis of active androgens that promote the progression of prostate cancer. AKR1C3 also contributes to androgen-independent cell proliferation and survival through the metabolism of prostaglandins and reactive aldehydes. Because of its elevation in castration-resistant prostate cancer (CRPC) tissues, AKR1C3 is a promising therapeutic target for CRPC. In this study, we found a novel potent AKR1C3 inhibitor, N -(4-fluorophenyl)-8-hydroxy-2-imino-2 H -chromene-3-carboxamide ( 2d ), and synthesized its derivatives with IC ₅₀ values of 25-56 nM and >220-fold selectivity over other AKRs (1C1, 1C2, and 1C4). The structural factors for the inhibitory potency were elucidated by crystallographic study of AKR1C3 complexes with 2j and 2l . The inhibitors suppressed proliferation of prostate cancer 22Rv1 and PC3 cells through both androgen-dependent and androgen-independent mechanisms. Additionally, 2j and 2l prevented prostate tumor growth in a xenograft mouse model. Furthermore, the inhibitors significantly augmented apoptotic cell death induced by anti-CRPC drugs (abiraterone or enzalutamide).