Design of Antituberculosis Agents that Target Siderophore Biosynthesis

描述(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)是由细菌病原体引起的世界上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络合剂(铁载体)负责从人类宿主获取铁，这一过程对结核杆菌的生存至关重要，因此分枝杆菌毒素已被提议作为结核病药物的新靶点。此外，分枝杆菌毒素可能是结核分枝杆菌的短期铁贮库。抑制mycobactin的生物合成有望阻止铁的获得，并可能破坏铁的动态平衡。我们建议开发一类针对铁载体生物合成的新型抗菌剂。这一应用的主要焦点将是微生物结核分枝杆菌；然而，也将继续研究革兰氏阴性鲍曼不动杆菌和肺炎克雷伯菌。在第一个具体目标中，我们将建立在我们对先导化合物5‘-O-[N-(水杨基)磺酰基]腺苷(SAL-AMS)的构效关系的大量知识的基础上，以改善药物处置性能。将对化合物进行研究，以确定其药代动力学特性，然后使用结核病小鼠模型在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的一系列新的非核苷抑制剂。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性能的测试。在最后一个子目标中，我们建议进行作用机制研究，以确定我们的典型铁载体抑制剂靶向的潜在靶外受体。在第三个特定目标中，我们建议合成一种新酶的过渡态抑制剂，该酶催化结核分枝杆菌铁载体生产的第一步生物合成。这些合理设计的抑制剂将被评价为酶抑制，与分子靶标共结晶，抗结核活性和毒性评价，最后将利用全细胞放射分析来探索它们的作用机制。预计在完成这项工作后，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，并可能额外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.