Wellcome Centre for Anti-Infectives Research, Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, DD1 5EH Dundee, United Kingdom.
Seattle Structural Genomics Center for Infectious Disease, Seattle, WA 98109.
Proc Natl Acad Sci U S A. 2019 Apr 2;116(14):7015-7020. doi: 10.1073/pnas.1814685116. Epub 2019 Mar 20.
Malaria and cryptosporidiosis, caused by apicomplexan parasites, remain major drivers of global child mortality. New drugs for the treatment of malaria and cryptosporidiosis, in particular, are of high priority; however, there are few chemically validated targets. The natural product cladosporin is active against blood- and liver-stage and in cell-culture studies. Target deconvolution in has shown that cladosporin inhibits lysyl-tRNA synthetase (KRS1). Here, we report the identification of a series of selective inhibitors of apicomplexan KRSs. Following a biochemical screen, a small-molecule hit was identified and then optimized by using a structure-based approach, supported by structures of both KRS1 and KRS (KRS). In vivo proof of concept was established in an SCID mouse model of malaria, after oral administration (ED = 1.5 mg/kg, once a day for 4 d). Furthermore, we successfully identified an opportunity for pathogen hopping based on the structural homology between KRS1 and KRS. This series of compounds inhibit KRS and and in culture, and our lead compound shows oral efficacy in two cryptosporidiosis mouse models. X-ray crystallography and molecular dynamics simulations have provided a model to rationalize the selectivity of our compounds for KRS1 and KRS vs. (human) KRS. Our work validates apicomplexan KRSs as promising targets for the development of drugs for malaria and cryptosporidiosis.
疟原虫和隐孢子虫病由顶复门寄生虫引起，仍是全球儿童死亡的主要原因。特别是治疗疟疾和隐孢子虫病的新药是重中之重；然而，具有化学验证的靶点却很少。天然产物克拉屈滨在细胞培养研究中对红内期和肝期均具有活性。 在对克拉屈滨的靶标进行剖析时，发现克拉屈滨抑制赖氨酸 tRNA 合成酶（KRS1）。在这里，我们报告了一系列对顶复门 KRS 具有选择性的抑制剂的鉴定。在进行生化筛选后，鉴定出一种小分子命中物，然后使用基于结构的方法进行优化，该方法得到了 KRS1 和 KRS（KRS）的结构支持。在疟原虫 SCID 小鼠模型中经口服给药（ED = 1.5 mg/kg，每天一次，共 4 天）后，建立了体内概念验证。此外，我们成功地基于 KRS1 和 KRS 之间的结构同源性确定了病原体跳跃的机会。该系列化合物在培养物中抑制 KRS 和 和 ，我们的先导化合物在两种隐孢子虫病小鼠模型中显示出口服疗效。X 射线晶体学和分子动力学模拟提供了一个模型，可合理说明我们的化合物对 KRS1 和 KRS 与（人）KRS 的选择性。我们的工作验证了顶复门 KRS 作为开发疟疾和隐孢子虫病药物的有前途的靶标。
