Novel Antibacterials Targeting Gram-negative Nonfermenters

描述（由申请人提供）：本项目的总体目标是开发一种新的化学类广谱治疗剂，双-（吲哚）铅系列，用于对抗革兰氏阴性非发酵菌。目前治疗的数量和有效性有限，药物开发管道中新型广谱抗生素的稀缺性以及这些细菌产生耐药性的容易性，都表明迫切需要开发能够对抗这些病原体的新的更有效，更广泛作用的抗菌剂。在这个新的化学系列化合物表现出广谱抗菌活性，显示出强大的（MIC的0.2-3？g/ml）抑制革兰氏阴性细菌物种的生长，包括革兰氏阴性非发酵菌如鲍氏不动杆菌、铜绿假单胞菌、洋葱伯克霍尔德氏菌和嗜麦芽窄食单胞菌。这些化合物还对苛养革兰氏阴性杆菌和大量来自肠杆菌科的菌株以及多种革兰氏阳性细菌物种具有活性。它们通过快速杀菌机制起作用，在接近MIC值的浓度下在1-4小时内显示出3个对数的杀灭。确切的作用机制尚不清楚;然而，铅系列已被证明可抑制透化细菌细胞中的DNA复制，并抑制纯化的细菌复制性DNA解旋酶。我们还不能分离出对主要先导支架MBX 1066或其类似物MBX 1162具有抗性的突变体。铅系列在革兰氏阴性感染的鼠模型中是有效的（即，鼠疫耶尔森氏菌、类鼻疽伯克霍尔德氏菌; ED 50 <10 mg/kg）。此外，化合物在小鼠中耐受良好（MTD =400 mg/kg）。最后，这些化合物合成相对容易且便宜，具有非常有利的商品成本。这些总体特征促进了这些化合物作为广谱抗菌剂用于对抗难治性革兰氏阴性细菌病原体的快速发展。我们将化学优化的双（吲哚）铅系列在一个合理的药物发现的努力，最初集中在提高广谱效力，同时最大限度地减少哺乳动物的细胞毒性。我们将在A.鲍曼不动杆菌引起的肺炎在本项目的II期，我们将使用至少两种大鼠感染模型（肺炎和皮囊）扩展体内表征，然后在两种适合IND提交的种属中进行IND使能（GLP）药代动力学、毒理学和安全药理学研究。公共卫生相关性：由革兰氏阴性非发酵菌（如鲍曼不动杆菌）引起的感染性疾病难以治疗，因为这些微生物中存在多药耐药性。它们越来越多地出现在医院和社区获得性感染以及在伊拉克和阿富汗战场上获得的感染中。该提案描述了一种合理的方法，通过创建更有效的化合物并测试它们的体外和体内活性，用双（咪唑啉吲哚）系列化合物（一系列有效的抗菌剂）靶向这些细菌制剂，这些化合物是由USAMRIID和Microbiotix的一个小组发现的。

DESCRIPTION (provided by applicant): The overall objective of this project is to develop a novel chemical class of broad-spectrum therapeutic agents, the bis-(indole) lead series, for use against Gram-negative nonfermenters. The limited number and efficacy of current therapies, the scarcity of novel broad-spectrum antibiotics in the drug development pipeline and the ease with which these bacteria develop drug resistance, argue for the urgent development of new more potent, broad-acting antibacterial agents capable of combating these pathogens. Compounds in this new chemical series exhibit broad-spectrum antibacterial activity, displaying potent (MIC's of 0.2-3 ?g/ml) inhibition of the growth of Gram-negative bacterial species, including such Gram-negative nonfermenters as Acinetobacter baumannii, Pseudomonas aeruginosa, Burkholderia cepacia and Stenotrophomonas maltophilia. These compounds are also active against fastidious Gram- negative bacilli and a large number of strains from the Enterobacteriaceae family as well as a variety of Gram-positive bacterial species. They act by a rapid bactericidal mechanism, exhibiting 3-log's of killing in 1-4 hours at concentrations near the MIC values. The precise mechanism of action is unknown; however, the lead series has been shown to inhibit DNA replication in permeabilized bacterial cells and to inhibit purified bacterial replicative DNA helicase. We have not been able to isolate mutants resistant to the primary lead scaffold MBX 1066 or its analog MBX 1162. The lead series is effective in murine models of Gram-negative infections (i.e., Yersinia pestis, Burkholderia pseudomallei; ED50 <10 mg/kg). In addition, the compounds are well-tolerated in mice (MTD =400 mg/kg). Finally, these compounds are relatively easy and inexpensive to synthesize, with a very favorable cost of goods. These overall characteristics advocate for the rapid development of these compounds as broad spectrum antibacterial agents for use against difficult-to-treat Gram-negative bacterial pathogens. We will chemically optimize the bis-(indole) lead series in a rational drug discovery effort focused initially on improving broad-spectrum potency while minimizing mammalian cytotoxicity. We will demonstrate efficacy in vivo in a murine model of A. baumannii-induced pneumonia. In Phase II of this project, we will expand upon the in vivo characterization with at least two rat infection models (pneumonia and skin pouch) and then conduct IND-enabling (GLP) pharmacokinetic, toxicology and safety pharmacology studies in two species suitable for IND submission. PUBLIC HEALTH RELEVANCE: Infectious disease caused by the Gram-negative nonfermenters, such as Acinetobacter baumannii, are difficult to treat due to the frequency of multi-drug resistance in these organisms. They are increasingly found in hospital and community-acquired infections as well as those infections obtained in the battlefields of Iraq and Afghanistan. This proposal describes a rational approach for targeting these bacterial agents with the bis-(imidazolinylindole) series of compounds, a series of potent antibacterials, discovered by a group at USAMRIID and Microbiotix, by creating more potent compounds and testing them for in vitro and in vivo activity.