Department of Pharmacology, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, United States.
Bioorg Med Chem Lett. 2012 May 15;22(10):3492-7. doi: 10.1016/j.bmcl.2012.03.085. Epub 2012 Mar 29.
Castrate resistant prostate cancer (CRPC) is associated with increased androgen receptor (AR) signaling often brought about by elevated intratumoral androgen biosynthesis and AR amplification. Inhibition of androgen biosynthesis and/or AR antagonism should be efficacious in the treatment of CRPC. AKR1C3 catalyzes the formation of potent AR ligands from inactive precursors and is one of the most upregulated genes in CRPC. AKR1C3 inhibitors should not inhibit the related isoforms, AKR1C1 and AKR1C2 that are involved in 5α-dihydrotestosterone inactivation in the prostate. We have previously developed a series of flufenamic acid analogs as potent and selective AKR1C3 inhibitors [Adeniji, A. O. et al., J. Med. Chem.2012, 55, 2311]. Here we report the X-ray crystal structure of one lead compound 3-((4-(trifluoromethyl)phenyl) amino)benzoic acid (1) in complex with AKR1C3. Compound 1 adopts a similar binding orientation as flufenamic acid, however, its phenylamino ring projects deeper into a subpocket and confers selectivity over the other AKR1C isoforms. We exploited the observation that some flufenamic acid analogs also act as AR antagonists and synthesized a second generation inhibitor, 3-((4-nitronaphthalen-1-yl)amino)benzoic acid (2). Compound 2 retained nanomolar potency and selective inhibition of AKR1C3 but also acted as an AR antagonist. It inhibited 5α-dihydrotestosterone stimulated AR reporter gene activity with an IC(50)=4.7 μM and produced a concentration dependent reduction in androgen receptor levels in prostate cancer cells. The in vitro and cell-based effects of compound 2 make it a promising lead for development of dual acting agent for CRPC. To illuminate the structural basis of AKR1C3 inhibition, we also report the crystal structure of the AKR1C3·NADP(+)·2 complex, which shows that compound 2 forms a unique double-decker structure with AKR1C3.
去势抵抗性前列腺癌（CRPC）与雄激素受体（AR）信号的增加有关，这种增加通常是由肿瘤内雄激素生物合成和 AR 扩增引起的。抑制雄激素生物合成和/或 AR 拮抗作用应该对 CRPC 的治疗有效。AKR1C3 催化从无活性前体形成强效 AR 配体，是 CRPC 中上调最明显的基因之一。AKR1C3 抑制剂不应抑制相关同工酶 AKR1C1 和 AKR1C2，它们参与前列腺内 5α-二氢睾酮的失活。我们之前开发了一系列芬那酸类似物作为强效和选择性 AKR1C3 抑制剂[Adeniji，AO 等人，J. Med. Chem.2012，55，2311]。在这里，我们报告了一种先导化合物 3-((4-(三氟甲基)苯基)氨基)苯甲酸（1）与 AKR1C3 复合物的 X 射线晶体结构。化合物 1 采用与芬那酸类似的结合取向，但其苯基氨基环更深入地进入亚口袋，从而赋予对其他 AKR1C 同工酶的选择性。我们利用了一些芬那酸类似物也作为 AR 拮抗剂的观察结果，并合成了第二代抑制剂，3-((4-硝基萘-1-基)氨基)苯甲酸（2）。化合物 2 保留了纳摩尔效力和对 AKR1C3 的选择性抑制作用，但也作为 AR 拮抗剂起作用。它抑制 5α-二氢睾酮刺激的 AR 报告基因活性，IC50=4.7 μM，并在前列腺癌细胞中导致雄激素受体水平的浓度依赖性降低。化合物 2 的体外和基于细胞的作用使其成为开发用于 CRPC 的双重作用剂的有前途的先导化合物。为了阐明 AKR1C3 抑制的结构基础，我们还报告了 AKR1C3·NADP(+)·2 复合物的晶体结构，该结构表明化合物 2 与 AKR1C3 形成独特的双层结构。
