Development of non-sedative, parasite-selective benzodiazepines to treat the neglected tropical disease schistosomiasis

摘要：被忽视的热带病血吸虫病是由寄生血吸虫引起的， 全球超过2.3亿人。目前的治疗仅依赖于一种药物，吡喹酮（PZQ）。PZQ是 对最近获得的尚未达到性成熟的寄生虫无效。PZQ也不杀人 直接给你。这些缺点，以及新出现的耐药寄生虫菌株的前景， 强调需要替代疗法来控制血吸虫病。长期目标是确定 改进的抗染色体药物。因此，本提案将研究一组替代化合物 具有抗寄生虫活性的苯二氮卓类药物苯二氮卓类药物可有效治疗 血吸虫病，但对引起镇静的人GABAAR具有高亲和力。的总体目标 本申请是鉴定一种杀真菌的苯并二氮杂，甲氯硝西泮的衍生物，其保留抗- 寄生活性，并且对引起镇静的GABAAR亚型缺乏亲和力。核心假设是， 减少宿主GABAAR参与的苯二氮卓类药物治疗将最大限度地减少镇静作用， 杀虫活性。这个项目的基本原理是，虽然宿主镇静是由药物作用驱动的， α1GABAAR，染色体基因组完全缺乏GABAAR。因此，GABAAR不能解释抗- 苯二氮卓类药物的寄生效应。相反，初步数据表明，甲氯安定作用于寄生虫 Ca 2+通道由于这种药物的“靶向”寄生虫受体和“脱靶”宿主受体是不同的， 应该有可能开发具有改进的选择性的处理。这将通过两个具体的 目的：1）开发对哺乳动物α 1GABAAR活性降低的甲氯硝西泮类似物。2)块 甲氯硝西泮与α 1 GABAAR拮抗剂混合的体内镇静作用。在第一个目标下，我们将 合成甲氯硝西泮类似物并筛选这些和其它亚型选择性苯并二氮杂 针对哺乳动物GABAAR的测定。然后筛选GABAAR亲和力降低的化合物 针对寄生虫体以鉴定寄生虫选择性衍生物。最后，将筛选杀真菌配体， 小鼠血吸虫病模型，以评估相对于甲氯硝西泮的疗效为基准。在第二 目的，我们将评估甲氯硝西泮的体内镇静作用（以及目标1的命中）和阻断作用。 α 1GABAAR选择性拮抗剂的镇静作用。旋转杆测试将用于确定镇静剂量 然后将其与不同比例的拮抗剂混合施用，以确定 一种混合物，能清除寄生虫，副作用最小。所提出的研究是有意义的 因为它将推动新的杀血吸虫药的发展--FDA还没有批准治疗血吸虫病的药物 从1982年开始这项研究是创新的，结合了陈博士在寄生虫学方面的专业知识， Cook博士是GABAAR亚型的基本性质和药理学方面的专家。

ABSTRACT: The neglected tropical disease schistosomiasis is caused by parasitic blood flukes that infect >230 million people worldwide. Current treatment is reliant on just one drug, praziquantel (PZQ). PZQ is ineffective against recently acquired parasites that have not reached sexual maturity. PZQ also does not kill schistosomes directly. These drawbacks, and the prospect of emerging treatment-resistant parasite strains, highlight the need for alternative therapies to control schistosomiasis. The long-term goal is to identify improved anti-schistosomal drugs. Therefore, this proposal will investigate an alternative group of compounds with proven anti-parasitic activity, benzodiazepines. Benzodiazepine leads are effective at treating schistosomiasis but have high affinity for the human GABAARs that cause sedation. The overall objective of this application is to identify derivatives of a schistocidal benzodiazepine, meclonazepam, that retain anti- parasitic activity and lack affinity for sedation-causing GABAAR sub-types. The central hypothesis is that that benzodiazepine therapies with decreased engagement of host GABAARs will minimize sedation and retain schistocidal activity. The rationale for this project is that while host sedation is driven by drug action at the α1GABAAR, schistosome genomes lack GABAARs entirely. Therefore, GABAARs cannot account for the anti- parasitic effects of benzodiazepines. Instead, preliminary data indicates that meclonazepam acts on parasite Ca2+ channels. Since the ‘on-target’ parasite receptor and ‘off-target’ host receptor for this drug are distinct, it should be possible to develop treatments with improved selectivity. This will be done by pursuing two specific aims: 1) Develop analogs of meclonazepam with decreased activity at mammalian α1GABAARs. 2) Block sedation in vivo by admixture of meclonazepam with α1GABAAR antagonists. Under the first aim, we will synthesize meclonazepam analogs and screen these and other sub-type selective benzodiazepines in binding assays against mammalian GABAARs. Compounds with decreased GABAAR affinity will then be screened against schistosomes to identify parasite-selective derivatives. Finally, schistocidal ligands will be screened in murine model of schistosomiasis to assess efficacy benchmarked relative to meclonazepam. In the second aim, we will assess the in vivo sedative effects of meclonazepam (as well as hits from Aim 1) and the blockade of sedation by α1GABAAR-selective antagonists. The rotarod test will be used to determine the sedating dose of each compound, which will then be administered in mixture with varying ratios of antagonists to determine an admixture that admixture clears parasites with minimized side effects. The research proposed is significant because it will advance new schistocidal leads – no drug to treat schistosomiasis has been FDA approved since 1982. This research is innovative, combining Dr. Chan’s expertise in parasitology with the medicinal chemistry expertise of Dr. Cook, an expert in fundamental properties and pharmacology of GABAAR subtypes.