Optimizing IMPDH inhibitors for the treatment of cryptosporidiosis

描述（由申请方提供）：隐孢子虫属，包括隐孢子虫。parvum和C.人是原生动物寄生虫，特别是对免疫功能低下的个体和幼儿构成健康威胁。这些生物也是潜在的生物恐怖主义制剂，可能使大量人口丧失能力。目前的治疗选择是有限的。常用的抗寄生虫药物是无效的，唯一FDA批准的药物效果不佳，疫苗也不可用。基因组分析显示，隐孢子虫物种依赖于肌苷5 '-单磷酸脱氢酶（IMPDH）生产鸟嘌呤核苷酸，因此，生存。此外，该寄生虫似乎通过侧向转移从ε-变形杆菌获得IMPDH基因，因此C. parvum IMPDH（CpIMPDH）与人类直系同源物高度分化。因此，选择性CpIMPDH抑制剂可以提供一种治疗隐孢子虫病的有效策略，对患者的毒性最小。迄今为止，已经鉴定了几种结构上不同的CpIMPDH抑制剂，其在细胞培养模型中表现出优异的酶促效力、对人IMPDH的选择性、抗寄生虫活性，并且对于一个化合物系列，在急性隐孢子虫病小鼠模型中表现出体内功效。这项拟议研究的总体目标是进一步完善CpIMPDH抑制剂，以在隐孢子虫病的急性和慢性小鼠模型中实现疗效，以支持选择性CpIMPDH抑制是这种原生动物感染的可行治疗策略的假设，为研究界提供关于体内疗效的最佳化合物性质的指导，并提供CpIMPDH作为分子靶标的进一步临床前验证。这些目标将通过以下三个具体目标来实现：1）CpIMPDH抑制剂的设计、合成和体外评价，以测定CpIMPDH抑制效力和选择性，C. parvum细胞培养感染模型和ADME性质（包括小鼠和人肠和肝微粒体稳定性、细胞摄取、流出和毒性以及UGT介导的葡萄糖醛酸化）; 2）评估CpIMPDH抑制剂的体内药代动力学和急性毒性性质，包括在未感染和C.细小病毒感染小鼠; 3）在隐孢子虫病的急性和慢性动物模型中评估优化的CpIMPDH抑制剂，评估粪便卵囊排泄和胃肠道大体和组织病理学。此外，还将检查CpIMPDH抑制剂对肠道细菌种群的影响，以更全面地评价药效学效应，因为许多细菌具有与CpIMPDH相似的IMPDH。该项目还将制定限制药物分布到胃肠道的策略。由于该策略可适用于其他胃肠道疾病， 如肠易激综合征和结肠癌，这项工作具有广泛的意义，超出了隐孢子虫病的治疗。

DESCRIPTION (provided by applicant): Cryptosporidium species, including C. parvum and C. hominis, are protozoan parasites that present a health threat particularly to immunocompromised individuals and young children. These organisms are also potential bio-terrorism agents that could incapacitate large populations. Current treatment options are limited. Commonly used antiparasitic drugs are ineffective, the only FDA-approved drug is poorly efficacious, and vaccines are unavailable. Genomic analysis has revealed that Cryptosporidium species rely on inosine 5'- monophosphate dehydrogenase (IMPDH) for producing guanine nucleotides and, hence, survival. It also appears that the parasite obtained its IMPDH gene from an ε-proteobacterium by lateral transfer, so C. parvum IMPDH (CpIMPDH) is highly diverged from the human orthologs. Therefore, selective CpIMPDH inhibitors may provide an effective strategy for the treatment of cryptosporidiosis with minimum toxicity to the patient. To date, several structurally distinct classes of CpIMPDH inhibitors have been identified that have demonstrated excellent enzymatic potency, selectivity over human IMPDH, anti-parasitic activity in a cell culture model and, for one compound series, in vivo efficacy in an acute cryptosporidiosis mouse model. The overall goals of this proposed study are to further refine CpIMPDH inhibitors to achieve efficacy in both acute and chronic mouse models of cryptosporidiosis to support the hypothesis that selective CpIMPDH inhibition is a viable treatment strategy for this protozoan infection, provide guidance for the research community with respect to optimal compound properties for in vivo efficacy and provide further pre-clinical validation of CpIMPDH as a molecular target. These goals will be achieved by pursuing three specific aims: 1) design, synthesis and in vitro evaluation of CpIMPDH inhibitors in assays of CpIMPDH inhibitory potency and selectivity, a C. parvum cell culture infection model and ADME properties (including mouse and human intestinal and liver microsome stability, cellular uptake, efflux and toxicity, and UGT-mediated glucuronidation); 2) assess the in vivo pharmacokinetic and acute toxicity properties of CpIMPDH inhibitors, including in vivo models of oral absorption and tissue distribution in both non-infected and C. parvum infected mice; 3) evaluate optimized CpIMPDH inhibitors in acute and chronic animal models of cryptosporidiosis assessing fecal oocyst excretion and gastrointestinal gross and histopathology. In addition, the impact of CpIMPDH inhibitors on commensal bacteria populations will also be examined to more fully evaluate pharmacodynamics effects, since many bacteria have IMPDHs that are similar to CpIMPDH. This project will also develop strategies for limiting drug distribution to the gastrointestinal tract. Since this strategy could be applicable to other gastrointestinal diseases, such as irritable bowel disease and colon cancer, this work has broad implications beyond the treatment of cryptosporidiosis.