Design of Antituberculosis Agents that Target Siderophore Biosynthesis

描述（由申请人提供）：由生长缓慢的结核分枝杆菌（Mtb）引起的结核病（TB）是世界上由细菌病原体引起的传染病死亡的主要原因。由于结核分枝杆菌（MTb）产生的这些小分子铁螯合剂（铁载体）负责从人类宿主获得铁，这一过程对结核分枝杆菌（MTb）的存活至关重要，分枝杆菌素已被提出作为结核病药物的新靶点。此外，分枝杆菌素可能在结核分枝杆菌中充当短期铁储存库。抑制菌素的生物合成有望阻断铁的获取并潜在地破坏铁的稳态。我们建议开发一类新的靶向铁载体生物合成的抗菌剂。这个应用程序的主要重点将是有机体结核分枝杆菌；然而，革兰氏阴性鲍曼不动杆菌和肺炎克雷伯菌也将继续研究。在第一个具体目标中，我们将建立我们的先导化合物5'- o -[N-（水杨基）磺胺酰]腺苷（Sal-AMS）的结构活性关系的实质性知识，以改善药物处置特性。将对化合物进行研究以确定药代动力学性质，然后在使用小鼠结核模型的体内感染模型中进行评估。此外，我们将探索1)新的类似物来证实我们假设的结合模型，2)具有改进的抗菌活性谱的类似物，以及3)从高通量筛选中鉴定出的一系列新的非核苷类抑制剂。在第二个具体目标中，将进行药代动力学研究，并在小鼠结核病模型中评估化合物。新合成的类似物还将进行酶抑制，抗菌活性和药物处置特性的分析。在最后的子目标中，我们建议进行作用机制研究，以确定我们的原型铁载体抑制剂靶向的潜在脱靶受体。在第三个具体目标中，我们提出合成一种新酶的过渡态抑制剂，该酶催化了结核分枝杆菌生产铁载体的第一个生物合成步骤。这些合理设计的抑制剂将被评估其酶抑制作用，与分子靶点共结晶，评估其抗结核活性和毒性，最后将通过全细胞放射测定来探索其作用机制。预计在完成这项研究后，我们将验证我们的假设，即铁载体介导的铁获取在体内是必不可少的。因此，本文提出的研究有望对人类健康产生积极影响，并可能进一步验证一类针对铁载体生物合成的新型抗生素。

DESCRIPTION (provided by applicant): Tuberculosis (TB) caused by the slow growing bacillus Mycobacterium tuberculosis (Mtb) is the leading cause of infectious disease mortality in the world by a bacterial pathogen. The mycobactins have been proposed as novel targets for TB drugs since these small-molecule iron-chelators (siderophores) produced by Mycobacterium tuberculosis (MTb) are responsible for obtaining iron from the human host, a process that is essential for the survival of MTb. Additionally, the mycobactins may serve as a short-term iron reservoir in Mtb. Inhibition of mycobactin biosynthesis is expected to block iron acquisition and potentially disrupt iron homeostasis. We propose to develop a new class of antibacterial agents that target siderophore biosynthesis. The primary focus of this application will be on the organism Mycobacterium tuberculosis; however, the Gram-negative Acinetobacter baumannii and Klebsiella pneumoniae will also be pursued. In the first specific aim we will build on our substantial knowledge of the structure activity relationships of our lead compound 5'-O-[N-(salicyl)sulfamoyl]adenosine (Sal-AMS) to improve drug disposition properties. Compounds will be investigated to determine pharmacokinetic properties and then evaluated in an in vivo model of infection using a murine model of TB. Additionally, we will explore 1) new analogues to confirm our hypothesized binding model, 2) analogues with an improved spectrum of antibacterial activity, and 3) a new series of nonnucleoside inhibitors identified from high-throughput screening. In the second specific aim, pharmacokinetic studies will be performed and compounds evaluated in a murine TB model. Newly synthesized analogues will also be assayed for enzyme inhibition, antibacterial activity, and drug disposition properties. In a final subaim, we propose to perform mechanism of action studies to identify potential off-target receptors targeted by our prototypical siderophore inhibitors. In the third specific aim, we propose to synthesize transitions-state inhibitors of a new enzyme, which catalyzes the first biosynthetic step in production of the siderophores from M. tuberculosis. These rationally designed inhibitors will be evaluated for enzyme inhibition, co-crystallized with the molecular target, evaluated for antitubercular activity and toxicity, and finally their mechanism of action will be explored using whole-cell radioassays. It is expected that upon completion of this we will have validated our hypothesis that siderophore-mediated iron acquisition is essential in vivo. Thus, the research proposed herein is expected to have a positive impact on human health and may additionally validate a new class of antibiotics that target siderophore biosynthesis. PUBLIC HEALTH RELEVANCE: Tuberculosis (TB) caused by the slow growing bacillus Mycobacterium tuberculosis (Mtb) is the leading cause of infectious disease mortality in the world by a bacterial pathogen. M. tuberculosis and other atypical mycobacteria are now classified as opportunistic infections of AIDS patients. The proposed research is expected to validate siderophore biosynthesis as new antibacterial target, which may lead to the development of a new class of antitubercular agents.