Targeting S-adenosylmethionine decarboxylase for HAT drug discovery

描述（由申请人提供）：非洲人类锥虫病（HAT）是由寄生原生动物布鲁氏锥虫引起的。HAT被列为世卫组织第1类疾病（新出现且不受控制），对非洲流行区域造成了巨大的卫生和经济负担。除非得到治疗，否则这种疾病是致命的，目前的治疗方法具有高毒性和困难的治疗方案。此外，目前没有一种药物对这种疾病的种类和阶段都有效。我们非常需要将寄生虫基本生物学的最新进展转化为新的安全有效的药物，这些药物对所有形式的寄生虫都有活性，并且易于施用。多胺是细胞生长所必需的代谢产物。多胺生物合成酶，包括鸟氨酸脱羧酶（ODC）和s -腺苷蛋氨酸脱羧酶（AdoMetDC）是寄生虫必需的。a-二氟甲鸟氨酸（DFMO）是一种ODC的自杀抑制剂，是晚期冈比亚锥虫的一线治疗方法，证实了多胺生物合成作为寄生虫的药物靶点。我们的团队已经系统地探索了多胺生物合成途径中其他酶的潜力，以验证新的抗锥虫药物的发现，从而验证了AdoMetDC作为HAT药物发现的一个非常有希望的靶点。我们使用遗传方法证明AdoMetDC对血期布氏体寄生虫至关重要，我们发现该酶受哺乳动物细胞中未发现的独特机制调节。从先前发现的人类AdoMetDC抑制剂（MDL 73811）开始，我们发现了新的化合物（例如Genz 644131），这些化合物是布鲁氏T. AdoMetDC的有效不可逆抑制剂，在体外对寄生虫具有nM活性，并且在早期小鼠感染模型中具有治愈性。然而，Genz 644131对小鼠晚期感染模型无效。我们的目标是确定新的布鲁氏T. AdoMetDC抑制剂，并围绕这些抑制剂进行先导优化程序，以确定具有治疗两种和两期HAT的潜力的临床前候选药物。我们制定了一项由两部分组成的战略，以最大限度地提高我们实现这一目标的机会。在Aim 1中，我们将对Genz 644131系列进行额外的先导优化工作，目标是在后期模型中识别具有改善脑穿透性和活性的化合物。在第二阶段，我们将进行高通量筛选（HTS）来鉴定新的布鲁氏杆菌AdoMetDC抑制剂。从HTS中鉴定的化合物将被验证，并根据靶标选择矩阵（包括效价、选择性、全细胞活性和合适的ADME特性）选择两个最佳系列。在第三部分中，我们将讨论一个顶级系列的迭代先导优化程序。在目标4中，将进行作用机制和耐药性研究，提供已确定候选药物适用性的支持数据。DNDi已同意担任该项目的项目顾问。

DESCRIPTION (provided by applicant): Human African trypanosomiasis (HAT) is caused by the parasitic protozoan, Trypanosoma brucei. HAT is listed as a WHO Category 1 disease (emerging and uncontrolled) that exerts a large burden in both health and economic costs to the endemic regions in Africa. The disease is fatal unless treated and current therapies suffer from high toxicity and difficult treatment regimes. Furthermore none of the current drugs are effective against both species and stages of the disease. There is a great need to translate recent advances in the understanding of the basic biology of the parasite into new safe, effective drugs that have activity against all forms of the parasite, and which can be easily administered. Polyamines are essential metabolites that are required for cell growth. The polyamine biosynthetic enzymes, including ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC) are essential to the parasite. a-difluoromethyornithine (DFMO), a suicide inhibitor of ODC, is the frontline treatment for late-stage T. gambiense, validating polyamine biosynthesis as a drug target in the parasite. Our group has systematically explored the potential for other enzymes in the polyamine biosynthetic pathway to be validated for the discovery of new anti-trypanosomal agents, leading to the validation of AdoMetDC as a highly promising target for HAT drug discovery. We demonstrated that AdoMetDC is essential to blood stage T. brucei parasites using genetic approaches and we discovered that the enzyme is regulated by a unique mechanism not found in mammalian cells. Starting from a previously identified human AdoMetDC inhibitor (MDL 73811) we identified new compounds (eg Genz 644131) that are potent irreversible inhibitors of T. brucei AdoMetDC, with nM activity against parasites in vitro, and that are curative in early stage mouse infection models. Genz 644131 however is not effective against late stage infection models in mice. Our objectives are to identify novel inhibitors of T. brucei AdoMetDC without this liability, and to undertake a lead optimization program around these inhibitors to identify a preclinical candidate with the potential to treat both species and both stages of HAT. We have developed a two-part strategy that should maximize the chances that we can achieve this goal. In Aim 1 we will undertake additional lead optimization work on the Genz 644131 series with the goal of identifying compounds with improved brain penetration and activity in the late stage model. In Aim 2 we will conduct a high throughput screen (HTS) to identify novel T. brucei AdoMetDC inhibitors. Compounds identified from the HTS will be validated, and two of the best series will be selected based on a target selection matrix that includes potency, selectivity, activity in whole cell assays and suitable ADME properties. An iterative lead optimization program of the top series will be prosecuted in Aim 3. In Aim 4 mechanism of action and resistance studies will be undertaken, providing supporting data on suitability of the identified candidates. DNDi has agreed to serve as program consultants on this project. Public Health Relevance: Human African sleeping sickness (HAT) is a fatal insect borne disease caused by a parasitic pathogen that leads to death if untreated. Current drug therapies have high toxicity and are difficult to administer in rural African settings where the disease is endemic. The goal of this proposal is to identify novel, safe and easily administered compounds that cure both early and late stage infections of this disease in animal models, resulting in the nomination of a preclinical development candidate for the treatment of HAT by the completion of the 5-year fund period.