Methylerythritol Phosphate Pathway-Specific Natural Products as Antibacterials

描述（由申请人提供）：该项目的长期目标是鉴定一类新的靶向甲基赤藓糖醇磷酸（MEP）途径的抗生素，这是一种对所有革兰氏阴性和许多革兰氏阳性细菌的生存能力至关重要的新途径。革兰氏阴性菌造成了一半以上的医院获得性（院内）感染，每年造成的损失估计为50亿美元，其中60%是由耐药菌引起的。每一种被CDC和NIAID描述为A、B或C类生物制剂的细菌病原体（革兰氏阴性和革兰氏阳性）都需要MEP途径才能存活。许多抗生素的过度使用/误用导致耐药性同时上升到危险水平。此外，已知或怀疑有几个国家已经开发出用于生物攻击的细菌制剂，其中一些制剂被改造成具有抗生素抗性。由于细菌不会受到导致耐药性的选择压力，预计未来几代现有抗生素的使用期限将比全新种类的抗生素更短。设计对未知抗生素的耐药性的能力也不太可能。类异戊二烯生物合成的MEP途径代表了开发抗生素的新靶点，具有比现有抗生素类别更大的增加效用的潜力。类异戊二烯生物合成是所有生物的基本过程。类异戊二烯是最多样化的天然产物之一，其大小从十碳单萜到天然橡胶（分子量为150万）不等，但它们是由两种五碳前体构成的：二磷酸异戊烯基（IPP）和二磷酸二甲基烯丙基（DMAPP）。对于IPP和DMAPP的生物合成，人类使用甲羟戊酸（MVA）途径，而所有革兰氏阴性和许多革兰氏阳性细菌都需要不相关的MEP途径。这种天然的途径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。目前只有一种靶向MEP通路的化合物进行了临床评估。因此，任何针对这一途径的化学实体都代表着一类全新的抗生素。Echelon Biosciences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通路的天然产物，这些天然产物可能会成为临床前开发候选化合物。这将通过以下目标来实现。首先，将完成体外生化分析，以确定途径中最后步骤的作用机制；其次，将使用经过验证的筛选平台进行修改，筛选MEP途径抑制剂的天然产物库；第三，描述由于撞击而观察到的抑制；第四，在筛选到的天然产物周围合成基于片段的化合物文库。公共卫生相关性：细菌对当前治疗方法的耐药性在社区和医院环境以及生物防御中至关重要。该项目将鉴定天然产物，专门阻断一种在人类中未发现的新型细菌途径。该途径不是目前任何处方治疗的靶点，因此，相对于目前使用的后续几代抗生素，这些化合物及其衍生物有望具有长期的效用。

DESCRIPTION (provided by applicant): The long-term objective of this project is to identify a new class of antibiotics targeting the methylerythritol phosphate (MEP) pathway, a novel pathway essential for the viability of all Gram-negative and many Gram- positive bacteria. 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. Every bacterial pathogen (Gram-negative and Gram-positive) described by the CDC and NIAID as Category A, B or C biological agents require the MEP pathway for survival. The overuse/misuse of many antibiotics has resulted in a concurrent rise in resistance to dangerous levels. Additionally, several nations are known or suspected to have developed bacterial agents for use in a biological attack with some of these agents engineered to be antibiotic resistant. Future generations of existing antibiotics 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 ability to engineer resistance to as of yet unknown antibiotics is also unlikely. The MEP pathway for isoprenoid biosynthesis represents a novel target for developing antibiotics with greater potential for increased utility over existing antibiotic classes. Isoprenoid biosynthesis is an essential process of all living organisms. Representing one of the most diverse classes of natural products, isoprenoids range in size from ten-carbon monoterpenes to natural rubber (molecular weight 1.5 million), yet they are constructed from two five-carbon precursors: isopententyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). For the biosynthesis of IPP and DMAPP, humans use the mevalonate (MVA) pathway while all Gram-negative and many Gram-positive bacteria require the unrelated MEP pathway. This natural pathway 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 chemical entity targeting this pathway represents an entirely new class of antibiotics. Echelon Biosciences will utilize a novel, proprietary whole-cell screening platform to identify natural products that specifically target the MEP pathway which could potentially lead to compounds as pre-clinical development candidates. This will be accomplished by the following aims. First, in vitro biochemical assays to determine mechanism of action for the last steps in the pathway will be completed; Second, a natural product library will be screened for MEP pathway inhibitors using a modification of a validated screening platform; Third, characterizing the inhibition observed as a result of hits; Fourth, synthesizing fragment-based libraries of compounds around natural products identified in the screen. PUBLIC HEALTH RELEVANCE: Resistance of bacteria to current therapeutics is of paramount importance in community and hospital settings as well as for biodefense. This project will identify natural products specifically blocking a novel bacterial pathway not found in humans. The pathway is not the target of any currently prescribed therapeutic, therefore these compounds and their derivatives are expected to have prolonged utility relative to subsequent generations of antibiotics presently in use.