Methylerythritol Phosphate Pathway Inhibitors Targeting Gram-Negative Infections

描述（由申请人提供）：该项目的长期目标是确定一类新的抗生素，其靶向对所有革兰氏阴性菌的生存力至关重要的未充分开发的途径，即磷酸甲脂酶（MEP）途径。超过一半的医院获得性（院内）感染是由革兰氏阴性细菌引起的，这些感染每年造成的损失估计为50亿美元，其中超过60%是由耐药细菌引起的。许多抗生素的过度使用导致耐药性同时上升到危险水平。预计未来几代现有抗生素类别的实用期将比全新类别的抗生素更短，因为细菌不会受到导致耐药性的选择压力。类异戊二烯生物合成的MEP途径代表了开发一类抗生素的新靶点，其具有比现有抗生素类更大的增加效用的潜力。类异戊二烯生物合成是所有生物体的基本过程。类异戊二烯代表了最多样化的天然产物类别之一，其具有多种结构特征，并且尺寸范围从十碳单萜到分子量高达150万的天然橡胶。尽管存在这种多样性，但所有类异戊二烯都是由两种五碳前体合成的：异戊烯基二磷酸（IPP）和二甲基烯丙基二磷酸（DMAPP）。在自然界中发现了IPP和DMAPP生物发生的两个不相关的途径。甲羟戊酸（MVA）途径存在于人类、一些革兰氏阳性细菌和植物的胞质溶胶中，而MEP途径被所有革兰氏阴性细菌、一些革兰氏阳性细菌和植物质体利用。这种天然分布和缺乏特异性靶向MEP途径的药物使其成为抗菌药物的理想新靶点。只有一种靶向MEP途径的化合物经过了临床评价，因此，任何靶向该途径的新化学实体都代表了一类全新的抗生素。Echelon将利用一种新型的专有全细胞筛选平台来鉴定特异性靶向MEP途径的化学试剂。这将通过以下方式实现：首先，开发用于表征MEP特异性抑制剂的生物化学工具（例如，确定MIC、IC50、酶靶标）。第二，调整经过验证的筛选平台，以允许针对途径中的每个步骤识别抑制剂。第三，筛选MEP通路抑制剂的化学多样性文库。第四，表征作为命中结果观察到的抑制。第五，在筛选中鉴定的支架周围合成化合物的聚焦文库，产生具有增加的效力的分子。第六，筛选在初始筛选中获得的命中物以杀死引起医院感染的革兰氏阴性细菌的能力。 在医院和社区环境中，细菌对当前抗生素的耐药性继续增加。该项目的目标是确定针对独特的未充分开发的途径的新型抗生素。由于没有选择压力使细菌对这些抗生素产生耐药性，因此预计本项目中鉴定的化合物将比当前抗生素的后续几代具有更长的效用。

DESCRIPTION (provided by applicant): The long-term objective of this project is to identify a new class of antibiotics targeting an underexploited pathway essential for the viability of all Gram-negative bacteria, the methylerythritol phosphate (MEP) pathway. Gram-negative bacteria are responsible for more than half of hospital acquired (nosocomial) infections which cost an estimated $5 billion dollars per year with >60% caused by resistant bacteria. The overuse of many antibiotics has resulted in a concurrent rise in resistance to dangerous levels. Future generations of existing antibiotic classes are expected to have shorter periods of utility than an entirely new class as bacteria will not have been subjected to selective pressure leading to resistance. The MEP pathway for isoprenoid biosynthesis represents a novel target for developing a class of antibiotic with greater potential for increased utility over existing antibiotic classes. Isoprenoid biosynthesis is an essential process of all living organisms. Isoprenoids represent one of the most diverse classes of natural products with a multitude of structural features and ranging in size from the ten-carbon monoterpenes to natural rubber with a molecular weight as high as 1.5 million. Despite this diversity, all isoprenoids are synthesized from two five-carbon precursors: isopententyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). Two unrelated pathways for the biogenesis of IPP and DMAPP are found in nature. The mevalonate (MVA) pathway is found in humans, some Gram-positive bacteria and the cytosol of plants, while the MEP pathway is utilized by all Gram-negative bacteria, some Gram-positives and plant plastids. This natural distribution and a dearth of agents specifically targeting the MEP pathway make it an ideal new target for antibacterials. Only one compound targeting the MEP pathway has undergone clinical evaluation, therefore, any new chemical entity targeting this pathway represents an entirely new class of antibiotics. Echelon will utilize a novel, proprietary whole-cell screening platform to identify chemical agents that specifically target the MEP pathway. This will be accomplished by: First, developing biochemical tools for characterizing MEP-specific inhibitors (e.g. determination of MIC, IC50, enzyme target). Second, adapting a validated screening platform to allow for the identification of inhibitors against every step in the pathway. Third, screening chemically diverse libraries for MEP pathway inhibitors. Fourth, characterizing the inhibition observed as a result of hits. Fifth, synthesizing focused libraries of compounds around the scaffolds identified in the screen resulting in a molecule(s) with increased potency. Sixth, screening hits obtained in initial screens for the ability to kill Gram-negative bacteria responsible for nosocomial infections. Bacterial resistance to current antibiotics continues to increase in both hospital and community settings. The goal of this project is to identify novel antibiotics targeting a unique, underexploited pathway. Since there has been no selective pressure for bacteria to become resistant to these antibiotics, it is expected that compounds identified in this project will have a longer duration of utility than subsequent generations of the current antibiotics.