Thymidylate synthase inhibitors for malaria

描述（由申请人提供）： 恶性疟原虫二氢叶酸还原酶-胸苷酸合酶（DHFR-TS）是抗疟药如乙胺嘧啶的既定药物靶标，其阻断DHFR功能。对DHFR-TS前体药物摄取和表达调控的基础研究表明，TS也可能是疟疾化疗的合适靶点。这一概念从疟疾DHFR-TS晶体结构的可用性和制药公司开发针对人类TS的药物化学以治疗癌症的巨大努力中获得了额外的灵感。 本计划项目申请的中心假设是，当在胸苷存在下使用时，基于叶酸的TS抑制剂将安全有效地用于疟疾化疗。这一假设基于几个关键概念和观察结果： 效力：先导化合物对TS酶的Ki约为1 nM，对寄生虫细胞的EC 50低于100 nM。 靶特异性：低至10 μ M的胸苷可对哺乳动物细胞提供完全保护。靶特异性：相反，10 μ M胸苷对疟原虫细胞没有保护作用。选择性脆弱性：疟疾细胞不能过度产生DHFR-TS蛋白对抗叶酸剂的反应。 选择性脆弱性：可能存在疟疾特异性TS结合的机会。减少发展障碍：即使没有胸苷增强，几种基于叶酸的TS抑制剂已经通过了用于癌症治疗的人体I、II和III期临床试验。 本计划项目有三个具体目标：（i）测试一组TS抑制剂对恶性疟原虫的效力和耐药性的出现;（ii）使用结构和计算工具产生改进的新TS抑制剂;（iii）测量TS抑制剂在小鼠中的有效性和安全性以及人体中的保护性胸苷水平。该研究团队提供了高度互补的经验，从物理生物化学到美国医院的疟疾临床试验。 该项目的成功完成将为在人类中测试疟疾特异性TS抑制剂奠定基础，并提供一个令人兴奋的机会，让人们有信心从基础科学到临床迈出不寻常的一步。

DESCRIPTION (provided by applicant): Plasmodium falciparum dihydrofolate reductase-thymidylate synthase (DHFR-TS) is an established drug target of antimalarials such as pyrimethamine, which blocks the DHFR function. Basic studies on uptake of prodrugs and regulation of expression of DHFR-TS suggest that TS may also be a suitable target for malaria chemotherapy. This concept has received additional inspiration from the availability of the malaria DHFR-TS crystal structure and from vast efforts by pharmaceutical companies to develop medicinal chemistry against human TS for treatment of cancer. The central hypothesis of the present Program Project application is that folate-based TS inhibitors will be safe and effective for malaria chemotherapy when used in the presence of thymidine. The hypothesis rests on several key concepts and observations: POTENCY: Lead compounds display Ki approximately 1 nM for TS enzyme and EC50 below 100 nM against parasite cells. TARGET SPECIFICITY: As little as 10 mu M thymidine offers complete protection to mammalian cells. TARGET SPECIFICITY: In contrast, 10 mu M thymidine offers no protection to Plasmodium cells. SELECTIVITY VULNERABILITY: Malaria cells cannot overproduce DHFR-TS protein in response to antifolates. SELECTIVITY VULNERABILITY: There may be opportunities for malaria-specific TS binding. REDUCED DEVELOPMENT BARRIERS: Even without thymidine augmentation, several folate-based TS inhibitors have passed human Phase I, II, and III clinical trials for cancer treatment. The present Program Project has three specific aims: (i) To test a battery of TS inhibitors against P. falciparum for potency and emergence of resistance; (ii) To generate improved new TS inhibitors using structural and computational tools; and (iii) To measure efficacy and safety of TS inhibitors in mice and protective thymidine levels in humans. The team of established investigators offers highly complementary experiences ranging from physical biochemistry to malaria clinical trials in a U.S. hospital. Successful completion of this project will set the stage for testing malaria-specific TS inhibitors in humans and provide an exciting opportunity to take the uncommon step from basic science to the clinic with confidence.