Nitrothiazolides:Broad-Spectrum Category B Anti-parasitic/bacterial Therapeutics

描述（由申请人提供）： 拟议工作的研究重点是开发第二代广谱5-硝基噻唑类药物，用于治疗B类优先食源性和水源性病原体微小隐孢子虫、溶组织内阿米巴、贾第鞭毛虫、空肠弯曲杆菌和梭菌。所有这些人类病原体共享一个共同的和必需的代谢酶的中央代谢，丙酮酸铁氧还蛋白氧化还原酶（PFOR）被认为是一个很好的药物靶标。我们发表的和初步的研究表明，仿制药硝唑尼特（NTZ），一种5-硝基噻唑，是FDA批准用于治疗由C。parvum和G.在所有的靶病原体中，PFOR通过一种新的机制选择性地抑制。机理研究表明，硝基噻唑阴离子解离的乙酰辅酶A和还原能力的形成，从而阻止磷酸硫胺素焦磷酸盐过渡中间体。在此过程中，NTZ被质子化为非活性形式。硝唑尼特的生物活性高度依赖于pH值，拟议研究的目标是开发在较低pH值下更有效的衍生物。开发第二代广谱治疗药物的管道方法包括以下具体目标：（i）由来自X-10的pKa和结构数据的知识驱动合成新的先导化合物。X射线晶体学和在中等通量PFOR 96孔测定中筛选抑制活性（IC 50和Ki）;（ii）筛选活性先导化合物的体外抗靶病原体生物活性（MIC，MBC，MLC）;（iii）确定动物感染模型中有效先导物的治疗功效;以及（iv）通过产品开发、毒理学和临床试验规模扩大来开发可行的候选药物。这种新型靶标和抑制机制的两个意想不到的注意事项是（i）发展耐药性的可能性低和（ii）针对肠道病原体的NAD-丙酮酸脱氢酶的弱活性-适应性和定殖效率的损失。这些研究的成功完成将产生第二代广谱硝基噻唑类药物，其生物利用度和对B类肠道寄生虫和细菌的效力增加（广谱抗寄生虫剂），可以在临床上评价其预防和初级治疗生物恐怖活动或自然事件引起的感染。

DESCRIPTION (provided by applicant): The research focus of the proposed work is to develop second generation broad spectrum 5-nitrothiazolide therapeutics against Category B priority food and water borne pathogens Cryptosporidium parvum, Entamoeba histolytica, Giardia intestinalis, Campylobacter jejuni and Clostridium spp. All of these human pathogens share a common and essential metabolic enzyme of central metabolism, pyruvate ferredoxin oxidoreductase (PFOR) that is recognized as a good druggable target. Our published and preliminary studies establish that generic drug nitazoxanide (NTZ), a 5-nitrothiazolide which is FDA approved for treatment of infections caused by C. parvum and G. intestinalis, selectively inhibits PFOR in all of the target pathogens by a novel mechanism. Mechanistic studies show that the nitrothiazolide anion dissociates the pyruvate-thiamine pyrophosphate transition intermediate and thereby blocking formation of acetyl-CoA and reducing power. In the process, NTZ is protonated to an inactive form. The biological activity of nitazoxanide is highly pH dependent and the goal of the proposed studies is to develop derivatives which are more potent at lower pH. The pipeline approach to developing second generation broad spectrum therapeutics includes the following specific aims: (i) synthesize new lead compounds driven by knowledge of pKa and structural data from X-ray crystallography and screen for inhibitory activity in medium throughput PFOR 96 well assay (IC50 and Ki); (ii)screen active leads for biological activity against target pathogens in vitro (MIC, MBC, MLC); (iii) determine therapeutic efficacy of potent leads in animal infection models; and (iv) progress viable candidate drugs through product development, toxicology and scale up for clinical trials. Two unexpected caveats of this novel target and inhibitory mechanism are (i) low likelihood for development of drug resistance and (ii) weak activity against the NAD-pyruvate dehydrogenase of enteric pathogens - loss of fitness and colonization efficiency. Successful completion of these studies will produce second generation broad spectrum nitrothiazolide therapeutics with increased bioavailability and potency against Category B intestinal parasites and bacteria (broad spectrum anti-diarrheal agent) that can be evaluated clinically for prophylaxis against and primary treatment of infections caused by bioterrorism activities or natural events.