Fusidic acid derivatization to enhance entry into Gram-negative pathogens

耐碳青霉烯类肠杆菌科、鲍曼不动杆菌和铜绿假单胞菌是 新出现的多重耐药革兰氏阴性细菌病原体。随着频率的增加，他们经常证明 无法治疗或只能用有毒的抗菌剂治疗。因此，疾病预防控制中心现在将这些生物体归类为 抗生素耐药性的最高威胁级别迫切需要新的抗感染策略。夫西地酸是一种 对沙门氏菌有活性类固醇抗生素。金黄色葡萄球菌包括耐甲氧西林菌株，M.肺结核， 和n.淋病它在人体中也具有极好的安全性，可以通过口服和口服给药。 静脉途径。然而，它不能穿透革兰氏阴性ESKAPE病原体的外膜， 因此，这些病原体对可达到的药物水平具有抗性。然而，实验在 与粘菌素和其他膜透化剂的组合表明，即使是最高的 产生耐碳青霉烯酶、耐粘菌素的肠杆菌科（表达NDM-1，KPC，VIM， 和/或MCR-1）以及A.鲍曼不动杆菌和铜绿假单胞菌对这种抗生素敏感，如果外膜 促进渗透。此外，还讨论了S.金黄色葡萄球菌结合并阻断 夫西地酸靶标（EF-Tu）对革兰氏阴性病原体无效。此外，目标修改- 基于阻力赋予显著的适应性成本。因此，革兰氏阴性菌中预先存在的耐药性是 预计可忽略不计，并且不可从革兰氏阳性微生物转移。最近所谓的eNTRy 规则已经定义了增强革兰氏阴性菌转化率的分子特性。基于本质上 令人信服的性质夫西地酸，我们建议使用新的逆合成半合成方法， 在夫西地酸类似物的开发过程中应用eNTRy规则，通过胺和氟取代。的 潜在的目标将是鉴定对革兰氏阳性菌和革兰氏阴性菌具有广谱活性的类似物， 革兰氏阴性病原体，并填补了关键的医疗需求。没有以前发表的努力沿着沿着这些 线，因此，拟议的工作是既新颖又创新。重要的是，类似物将是 在一系列互补功能研究中进行了分析。这些将包括体外和体内 区分辐射和活动影响的测量;活动谱研究;以及 代谢稳定性评估;耐药倾向和毒理学，这将有助于对化合物进行排名， 进一步深入探索。这项为期两年的探索性R21提案的近期目标是解决 eNTRy规则的逆合成应用在鉴定易处理的、有效的、广谱的夫西地酸方面的潜力 类似物值得进一步探索。

Carbapenem-resistant Enterobacteriaceae, Acinetobacter baumannii, and Pseudomonas aeruginosa are emerging multidrug-resistant Gram-negative bacterial pathogens. With increasing frequency, they often prove untreatable or treatable only with toxic antimicrobials. Therefore, the CDC now categorizes such organisms in their top antibiotic resistance threat level. New anti-infective strategies are urgently needed. Fusidic acid is a steroid antibiotic that has activity against S. aureus inclusive of methicillin-resistant strains, M. tuberculosis, and N. gonorrhoeae. It also has an excellent safety profile in humans and can be given by both by oral and intravenous routes. However, it does not penetrate the outer membrane of Gram-negative ESKAPE pathogens, and, therefore, these pathogens are resistant to achievable drug levels. However, experiments performed in combination with colistin and other membrane-permeabilizing agents indicate that even the most highly resistant carbapenemase-producing, colistin-resistant Enterobacteriaceae (expressing NDM-1, KPC, VIM, and/or MCR-1) and also A. baumannii and P. aeruginosa are susceptible to this antibiotic, if outer membrane penetration is facilitated. Further, the major circulating resistance elements in S. aureus that bind to and block the fusidic acid target (EF-Tu) are ineffective against Gram-negative pathogens. Further, target modification- based resistance confers a significant fitness cost. Therefore, pre-existing resistance in Gram-negatives is predicted to be negligible, and non-transferable from Gram-positive organisms. Recently so-called eNTRy rules have defined molecular properties that enhance penetrance into Gram-negatives. Based on intrinsically compelling properties of fusidic acid, we propose to use novel retrosynthetic semi-synthesis approaches to apply eNTRy rules during development of fusidic acid analogues, via amine and fluorine substitution. The underlying goal will be to identify analogues that have broad-spectrum activity against both Gram-positive and Gram-negative pathogens and fill a critical medical need. There are no previously published efforts along these lines, and, therefore, the proposed work is both novel and innovative. Importantly, the analogues will be profiled in a series of complementary functional studies. These will include both in vitro and in vivo measurements that will distinguish effects of penetrance and activity; activity spectrum studies; and assessment of metabolic stability; resistance propensity, and toxicology that will help rank compounds for further intensive exploration. The near-term goal of this two-year, exploratory R21 proposal is to address potential of retrosynthetic application of eNTRy rules to identify tractable, potent, broad-spectrum fusidic acid analogues worthy of further exploration.