Small Molecule Discovery Center, University of California San Francisco, 1700 4th Street, San Francisco, CA, 94158, USA ; Department of Pharmaceutical Chemistry, University of California San Francisco, 1700 4th Street, San Francisco, CA, 94158, USA ; Department of Cellular and Molecular Pharmacology, University of California San Francisco, 1700 4th Street, San Francisco, CA, 94158, USA.
Beilstein J Org Chem. 2013;9:15-25. doi: 10.3762/bjoc.9.3. Epub 2013 Jan 4.
Inhibition of the Trypanosoma cruzi cysteine protease cruzain has been proposed as a therapeutic approach for the treatment of Chagas' disease. Among the best-studied cruzain inhibitors to date is the vinylsulfone K777 (1), which has proven effective in animal models of Chagas' disease. Recent structure-activity studies aimed at addressing potential liabilities of 1 have now produced analogues such as N-[(2S)-1-[[(E,3S)-1-(benzenesulfonyl)-5-phenylpent-1-en-3-yl]amino]-3-(4-methylphenyl)-1-oxopropan-2-yl]pyridine-4-carboxamide (4), which is trypanocidal at ten-fold lower concentrations than for 1. We now find that the trypanocidal activity of 4 derives primarily from the inhibition of T. cruzi 14-α-demethylase (TcCYP51), a cytochrome P450 enzyme involved in the biosynthesis of ergosterol in the parasite. Compound 4 also inhibits mammalian CYP isoforms but is trypanocidal at concentrations below those required to significantly inhibit mammalian CYPs in vitro. A chemical-proteomics approach employing an activity-based probe derived from 1 was used to identify mammalian cathepsin B as a potentially important off-target of 1 and 4. Computational docking studies and the evaluation of truncated analogues of 4 reveal structural determinants for TcCYP51 binding, information that will be useful in further optimization of this new class of inhibitors.
抑制克氏锥虫半胱氨酸蛋白酶 cruzain 已被提议作为治疗恰加斯病的一种治疗方法。迄今为止，研究最多的 cruzain 抑制剂之一是 vinylsulfone K777（1），它已被证明在恰加斯病的动物模型中有效。最近针对 1 的潜在缺陷的结构活性研究现已产生了类似物，例如 N-[(2S)-1-[[(E,3S)-1-(苯磺酰基)-5-苯基戊-1-烯-3-基]氨基]-3-(4-甲基苯基)-1-氧代丙-2-基]吡啶-4-甲酰胺（4），其杀变形虫活性比 1 低十倍。我们现在发现，4 的杀变形虫活性主要源于对 T. cruzi 14-α-脱甲基酶（TcCYP51）的抑制，这是一种参与寄生虫中麦角固醇生物合成的细胞色素 P450 酶。化合物 4 还抑制哺乳动物 CYP 同工酶，但在体外抑制哺乳动物 CYP 的浓度以下具有杀变形虫活性。使用源自 1 的基于活性的探针的化学蛋白质组学方法被用于鉴定哺乳动物组织蛋白酶 B 作为 1 和 4 的潜在重要非靶标。计算对接研究和 4 的截断类似物的评估揭示了与 TcCYP51 结合的结构决定因素，这些信息将有助于进一步优化这一新类抑制剂。
