Small Molecule Inhibitors of Anthrax Lethal Factor

描述（由申请人提供）：炭疽芽孢杆菌的雾化孢子是对美国安全最严重的生物恐怖主义威胁之一。基于新型化学支架的新疗法对生物防御武器库至关重要，因为它们可能对天然和工程抗性形式的炭疽杆菌都有效。我们的策略是建立有效的炭疽治疗方法，不是通过针对生物体的生存能力，而是通过直接针对发病机制。为了实现这一目标，我们通过化学文库筛选和3D子结构数据库挖掘相结合，确定了类似药物的小分子LF抑制剂。在酶促试验中，这些抑制剂已被证明能以低M效与LF特异性结合，并保护巨噬细胞免受含毒素LF的攻击。所确定的抑制剂类别是新颖的，并且缺乏非药物样特征，例如在许多已知的蛋白酶抑制剂中常见的羟肟酸和肽骨架。因此，这个经过验证的热门系列构成了开发有效、安全和口服生物可利用的抗炭疽药物的基础。为了进一步提高项目的成功概率，我们解决了结合在LF活性位点的抑制剂的x射线结构，从而为我们通过基于结构的药物设计来指导抑制剂的优化过程提供了有力的工具。该项目的总体目标是开发一种小分子LF抑制剂来治疗炭疽。在第一阶段，我们将应用药物和组合化学的成熟技术；抑制剂-酶复合物x射线晶体学和基于结构的药物设计（SBDD），以快速合成和评估这种新验证的热门系列的衍生物。在迭代过程中，我们将通过测量衍生物的酶、细胞活性和特异性来探测重点化合物文库，以寻找有助于更紧密结合和更有效抑制LF的特征。我们将确定与LF活性位点结合的改进抑制剂的x射线结构，并使用这些数据开发完善的药效团模型，以指导进一步探索结构活性关系（SAR）。此外，我们将评估化合物的最佳ADME（吸收，分布，代谢，消除）特性（例如，肝微粒体稳定性，Cyp异构体抑制和Caco2渗透性）。将在1-2 g水平合成具有足够酶促、细胞效力和ADME特性的化合物，并在LF诱导的大鼠死亡模型中测试其功效。从lf诱导的死亡中成功拯救大鼠将使化合物成为体内验证的先导物。在II期，我们将进一步评估这些先导物在两个物种中的体内疗效、药代动力学特性、毒性和安全性药理学，以便将它们发展成为ind前临床候选药物，适合人类临床试验（III期）。

DESCRIPTION (provided by applicant): Aerosolized spores of Bacillus anthracis represent one of the most serious bio-terrorist threats to the security of the United States. New therapeutics based upon novel chemical scaffolds are vital to the biodefense armory because they are likely to be effective against both natural and engineered resistant forms of B. anthracis. Our strategy is to build effective anthrax therapeutics not by targeting the viability of the organism but by targeting the mechanism of pathogenesis directly. Toward this aim, we have identified drug-like small molecule LF inhibitors through a combination of screening of chemical libraries and 3D sub-structure database mining. These inhibitors have been shown to specifically bind to LF with low (M potencies in enzymatic assays and to protect macrophages against challenge with toxin containing LF. The identified inhibitor classes are novel and devoid of non-drug like features such as the hydroxamic acid and peptidic backbone, which are common in many known protease inhibitors. Thus, this validated hit series forms the basis for development of efficacious, safe and orally bioavailable drugs against anthrax. To further enhance the probability of success of this project, the X-ray structure of the inhibitor bound in the active site of LF has been solved thus providing a powerful tool, which we will use to guide the inhibitor refinement process through structure-based drug design. The overall goal of this project is to develop a small molecule LF inhibitor to treat anthrax. In Phase I, we will apply proven techniques of medicinal and combinatorial chemistry; inhibitor-enzyme complex X-ray crystallography and structure-based drug design (SBDD) to rapidly synthesize and evaluate derivatives of this new validated hit series. In an iterative process, we will probe focused compound libraries for features contributing to tighter binding and more potent inhibition of LF by measuring the enzymatic, cellular activity and specificity of derivatives. We will determine the X-ray structures of improved inhibitors bound to the LF active site, and use these data to develop refined pharmacophore models to guide further probing of the structure activity relationship (SAR). In addition, we will assess compounds for optimal ADME (Absorption, Distribution, Metabolism, Elimination) properties (e.g., liver microsome stability, Cyp isoform inhibition and Caco2 permeability). Compounds with sufficient enzymatic, cellular potency and ADME properties will be synthesized at the 1-2 g level and tested for efficacy in a LF induced rat death model. Successful rescue of rats from LF-induced death will qualify compounds as in vivo-validated leads. In Phase II, we will further evaluate these leads for in vivo efficacy, pharmacokinetic properties, toxicity and safety pharmacology, in two species, in order to develop them into pre-IND clinical candidates, suitable for human clinical trials (Phase III).