Propargyl-linked Antifolates Targeting Klebsiella pneumoniae

描述(申请人提供)：由肠杆菌科引起的感染，主要是革兰氏阴性病原体肺炎克雷伯氏菌和大肠埃希菌，由于对包括青霉素、头孢菌素、碳青霉烯类、氟喹诺酮类和抗叶酸类在内的几类抗生素的广泛抗药性，正变得越来越难以治疗。除了耐药性，对革兰氏阴性病原体有效的天然有限的一系列药物，以及制药业缺乏抗生素发现，共同创造了对新药发现的迫切需求。在过去的几年里，我们利用基于结构的努力开发了一系列新的炔丙基连接的抗叶酸，它能有效地抑制基本酶二氢叶酸还原酶(DHFR)，并对革兰氏阳性和真核病原体有效。此外，这些化合物表现出低抵抗率和良好的物理化学性质。最近，我们发现炔丙基连接的抗叶酸在培养中对肺炎克雷伯菌有很强的抑制作用，对肺炎克雷伯菌的DHFR也有抑制作用。在这里，我们建议将这类抗叶酸扩大成为治疗致病性肠杆菌科细菌的优秀抗生素。我们提出了三个具体目标。在第一个目标中，我们将开发对肺炎克雷伯菌和大肠杆菌DHFR具有高效和选择性抑制作用的抑制剂，以及对野生型和耐药肠杆菌科细菌的有效抑制物，如甲氧苄氨嘧啶、ESBL-、KPC-和NDM1-变异体，同时保持较低的人体细胞毒性。在第二个目标中，我们将确定野生型和耐甲氧普林的肠杆菌科DHFRs以及人DHFR的迭代晶体结构，旨在推动有效和选择性化合物的设计。第三个目标将集中在动物研究上：一系列有效化合物的初始阶段始于对野生型菌株的疗效评估和初始药代动力学参数。第二阶段将评估针对一系列表型的疗效以及详细的药代动力学/药效学参数。在这项提案的最后，我们希望提供一种高效的、口服的抗叶酸抗生素来对抗广泛的肠杆菌科分离株。

DESCRIPTION (provided by applicant): Infections caused by Enterobacteriaceae, primarily the Gram-negative pathogens Klebsiella pneumoniae and Escherichia coli, are becoming increasingly difficult to treat owing to widespread resistance to several classes of antibiotics including penicillins, cephalosporins, carbapenems, fluoroquinolones and antifolates. Along with resistance, the naturally limited array of agents effective against Gram-negative pathogens and the dearth of antibiotic discovery in the pharmaceutical industry combine to create a critical need for new drug discovery. For the past several years, we have used a structure-based effort to develop a novel series of propargyl-linked antifolates that potently inhibit the essential enzyme dihydrofolate reductase (DHFR) and are effective against Gram-positive and eukaryotic pathogens. Additionally, these compounds show low rates of resistance and have good physicochemical properties. Recently, we have discovered that the propargyl-linked antifolates are potent inhibitors of K. pneumoniae in culture and against K. pneumoniae DHFR. Here, we propose to extend this class of antifolates to become excellent antibiotics against pathogenic Enterobacteriaceae. We propose three specific aims. In the first aim, we will develop inhibitors that are potent and selective inhibitors of K. pneumoniae and E. coli DHFR and potent inhibitors of wild-type and resistant Enterobacteriaceae, such as trimethoprim-, ESBL-, KPC- and NDM1-variants while maintaining low human cell toxicity. In the second aim, we will determine iterative crystal structures of wild-type and trimethoprim-resistant Enterobacteriaceae DHFRs as well as human DHFR, intended to drive the design of potent and selective compounds. The third aim will focus on studies in animals: an initial stage with a set of potent compounds begins with the evaluation of efficacy against wild-type strains and initial pharmacokinetic parameters. A second stage will evaluate efficacy against a range of phenotypes along with detailed pharmacokinetic/pharmacodynamic parameters. At the end of this proposal we expect to deliver a highly efficacious, orally available antifolate antibiotic against a broad range of Enterobacteriaceae isolates.