Drug Discovery from Slow Growing and Rare Microbial Species

描述（由申请人提供）：该项目的总体目标是发现新的抗生素来对抗重要的耐药病原体。对于金黄色葡萄球菌MRSA、耐万古霉素肠球菌（VRE）、耐多药铜绿假单胞菌、鲍曼假单胞菌、ESBL和新德里产金属-b-内酰胺酶肠杆菌科以及结核分枝杆菌等病原体，我们的治疗方案正在用尽。在过去的30年里，只有3种新型抗生素被引入——利奈唑胺、达托霉素和非达霉素。利奈唑胺和非达霉素是在60年代被发现的，但当时并没有足够的吸引力。以这样的发现速度，耐药性上升也就不足为奇了。越来越明显的是，抗生素发现的瓶颈是缺乏良好的起始化合物。合成化合物文库的HTS中没有一种药物。放线菌产生的次生代谢物是抗生素的主要来源，但这一资源被过度开采。与此同时，还有一个潜在的非常大的未开发的天然产物来源——以前未培养的细菌构成了绝大多数细菌种类。需要数月才能在培养皿中形成菌落的生长缓慢的物种是这一多数的重要组成部分。我们推断，生长缓慢的细菌实际上可能代表休眠形式的细菌，在重新接种后会迅速生长。大多数生长缓慢的植物确实可以在重新接种后迅速培养，许多分离株代表以前未知的物种和属。在第一阶段，我们开发了一种方法，通过将单个细胞放置在微滴板的孔中，同时分离和培养缓慢的种植者。对5000个分离株进行筛选，产生了3种新的抗菌化合物，其中包括专门针对结核分枝杆菌的Novo23。Novo23的靶标是必不可少的分枝杆菌ClpP蛋白酶的ClpC1亚基。Novo23具有较低的细胞毒性，良好的耐受性和小鼠血液水平。我们将检验Novo23在小鼠结核模型中的疗效。进一步开发我们的三种新型抗菌药物是第二阶段的主要重点。然而，我们认识到，只有一小部分铅能制成药物。因此，我们还将进行大规模的发现工作，以确定将进入验证的其他抗菌剂

DESCRIPTION (provided by applicant): The overall goal of this project is to discover novel antibiotics to combat important drug-resistant pathogens. We are running out of treatment options for pathogens such as S. aureus MRSA, vancomycin-resistant Enterococci (VRE), multidrug-resistant P. aeruginosa, A. baumannii, ESBL and New Delhi metallo-b- lactamase-producing Enterobacteriaceae, and M. tuberculosis. Only 3 novel antibiotics have been introduced in the past thirty years - linezolid, daptomycin, and fidaxomicin. Linezolid and fidaxomicin were discovered in the 60s, but did not appear sufficiently attractive at the time. With this pace of discovery, it is not surprising that resistance is on the rise. It is becoming increasingly apparent that the bottleneck in antibiotic discovery is the lack of good starting compounds. Not a single drug came out of HTS of synthetic compound libraries. Secondary metabolites produced by actinomycetes have been the main source of antibiotics, but this resource was over mined. At the same time, there is a potentially very large untapped source of natural products - previously uncultured bacteria that make up the vast majority of all bacterial species. Slow- growing species that require months to form colonies on a Petri dish are an important component of this majority. We reasoned that slow growers may actually represent dormant forms of bacteria, and will rapidly grow upon reinoculation. The majority of slow growers can indeed be rapidly cultured upon reinoculation, and many of the isolates represent previously unknown species and genera. In Phase I, we developed a method to simultaneously isolate and culture slow growers by placing individual cells in wells of a microtiter plate. Screening 5,000 of these isolates produced 3 new antimicrobial compounds, including Novo23 that acts specifically against M. tuberculosis. The target of Novo23 is the ClpC1 subunit of the essential mycobacterial ClpP protease. Novo23 has low cytotoxicity, favorable tolerability and blood levels in mice. We will examine efficacy of Novo23 in mouse models of tuberculosis. Further development of our three novel antibacterials are a major focus of Phase II. However, we recognize that only a small fraction of leads makes it to a drug. Thus, we will also undertake a large-scale discovery effort to identify additional antibacterials which will enter validation as they become available. Novel compounds will be examined for spectrum, potency, resistance development, stability, mechanism of action, and novelty of structure. Leads that emerge will be tested in mouse models of infection. The end result of Phase II will be three lead compounds showing efficacy in animal models. This will enable subsequent preclinical development towards an IND, clinical studies, and FDA approval of a new therapeutic. We believe this strategy - advancing leads while backing them with a discovery pipeline - greatly increases the chances for the project's success.