Methylerythritol Phosphate Pathway-Specific Natural Products as Antibacterials

描述(申请人提供)：该项目的长期目标是确定一种新的针对甲基赤藓糖醇磷酸(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至关重要的新途径。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。CDC和NIAID将每一种细菌病原体(革兰氏阴性和革兰氏阳性)描述为A、B或C类生物制剂，都需要MEP途径才能生存。许多抗生素的过度使用/误用导致对危险水平的抗药性同时上升。此外，已知或怀疑有几个国家已开发出用于生物攻击的细菌剂，其中一些已被设计为具有抗生素抗药性。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将比全新类别的抗生素短。到目前为止，对未知抗生素产生抗药性的能力也不太可能。类异戊二烯生物合成的MEP途径是开发抗生素的新目标，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。类异戊二烯代表着最多样化的天然产物之一，其大小从十碳单萜烯到天然橡胶(相对分子质量为150万)不等，但它们是由两个五碳前体组成的：异戊二磷酸(IPP)和二甲基烯丙基二磷酸(DMAPP)。对于IPP和DMAPP的生物合成，人类使用甲羟戊酸(MVA)途径，而所有革兰氏阴性菌和许多革兰氏阳性菌都需要无关的MEP途径。这种自然途径的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化学实体都代表着一种全新的抗生素类别。梯队生物科学公司将利用一种新颖的、专有的全细胞筛选平台来识别专门针对MEP途径的天然产品，这可能会导致化合物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，以确定途径最后步骤的作用机制；其次，将使用经过验证的筛选平台的改进来筛选MEP途径抑制剂的天然产物文库；第三，表征HITS所观察到的抑制作用；第四，合成筛选中确定的天然产物周围的基于片段的化合物文库。公共卫生相关性：细菌对当前疗法的抗药性在社区和医院环境以及生物防御中至关重要。该项目将识别天然产品，专门阻断人类没有发现的一种新的细菌途径。该途径不是目前任何处方治疗的目标，因此这些化合物及其衍生物有望相对于目前使用的后续几代抗生素具有更长的实用价值。

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.