Methylerythritol Phosphate Pathway Inhibitors Targeting Gram-Negative Infections

描述(申请人提供)：该项目的长期目标是确定一类新的抗生素，目标是对所有革兰氏阴性细菌的生存至关重要的一种未被充分利用的途径，即甲基赤藓糖醇磷酸(MEP)途径。在医院获得性感染中，有一半以上是由革兰氏阴性菌引起的，这些感染每年造成的成本估计为50亿美元，其中60%是由耐药细菌引起的。许多抗生素的过度使用导致对危险水平的抗药性同时上升。现有抗生素类别的未来几代预计将比全新类别的使用期限更短，因为细菌将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目标，该类抗生素具有比现有抗生素类更大的实用潜力。类异戊二烯的生物合成是所有生物体必不可少的过程。类异戊二烯是最多样化的天然产物之一，具有多种结构特征，大小从十碳单萜烯到分子量高达150万的天然橡胶不等。尽管有这样的多样性，所有的异戊二烯类化合物都是由两个五碳前体合成的：异戊二磷酸(IPP)和二甲基烯丙基二磷酸(DMAPP)。在自然界中发现了IPP和DMAPP两条互不相关的生物发生途径。甲氧戊酸(MVA)途径存在于人类、一些革兰氏阳性菌和植物胞浆中，而MEP途径则被所有革兰氏阴性菌、一些革兰氏阳性菌和植物质体所利用。这种自然分布和缺乏专门针对MEP途径的药物使其成为抗菌药物的理想新靶点。只有一种针对MEP途径的化合物进行了临床评估，因此，任何针对这一途径的新化学实体都代表着一类全新的抗生素。梯队将利用一种新颖的、专有的全细胞筛选平台来识别专门针对MEP途径的化学制剂。这将通过以下方式实现：第一，开发用于表征MEP特异性抑制物的生化工具(例如，MIC、IC50、酶靶标的测定)。第二，调整一个有效的筛选平台，以便针对途径中的每一步识别抑制剂。第三，筛选不同化学成分的MEP途径抑制剂文库。第四，表征作为命中结果观察到的抑制。第五，在屏幕上确定的支架周围合成有焦点的化合物文库，从而产生具有更强效力的分子(S)。第六，筛选在初始筛查中获得的命中结果，以确定是否有能力杀死导致医院感染的革兰氏阴性细菌。 细菌对当前抗生素的耐药性在医院和社区环境中继续增加。该项目的目标是确定针对一种独特的、未被开发的途径的新型抗生素。由于细菌不存在对这些抗生素产生抗药性的选择压力，预计该项目中确定的化合物的使用期限将比当前抗生素的后续几代更长。

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.