Cheminformatic Discovery of Alternative Pathway C3 Pro-Convertase Inhibitors

描述（由申请人提供）：尽管补体是先天免疫系统的支柱，但不适当或不受控制的补体激活水平是导致人类炎症性疾病迅速增加的主要因素。然而，尽管补体应答的治疗操作在临床上非常重要，但只有有限的FDA批准的药物和适应症存在特异性靶向 补体系统中的活性成分。补体靶向治疗剂缺乏的主要因素是蛋白质的大尺寸和作为补体活性基础的分子识别事件的复杂性质。这使得科学家们很难确定哪些特定点最容易进行治疗干预。相比之下，细菌病原体金黄色葡萄球菌（Staphylococcus aureus）部署了一系列蛋白质，这些蛋白质在宿主/病原体共进化的过程中已经被天然选择和精细优化，以有效地阻断补体级联中的基本事件-特别是驱动补体应答扩增的多亚基AP C3转化酶的形成。因此，模拟葡萄球菌毒力蛋白活性的分子有望用于补体导向的抗炎治疗。 我们最近研究了使用新的化学信息学工具来鉴定与S的SCIN家族相同的C3 b位点结合的小分子的潜力。金黄色葡萄球菌补体抑制剂。虽然是在中试规模上进行的，但这项工作强烈表明，计算机模拟方法是筛选特异性靶向C3 b上功能重要位点的药物样化合物的新化学型的可行方法。在这项研究中，我们的目标是应用相同的化学信息学方法来筛选高度精细（约2000万）的化合物库，并鉴定在AP C3转化酶形成的初始步骤中结合具有已知作用的C3 b位点的小分子。这一步骤产生了一种称为AP C3前转化酶的结构，是该途径中被多个分泌型S家族破坏的同一点。金黄色葡萄球菌补体抑制剂（包括SCIN）。因此，我们认为AP C3前转化酶的形成是补体介导的炎症反应中药理学干预的生物学验证靶标。 本申请中描述的研究计划包括三个不同的具体目标。每个目标都有一个明确的结果，该结果基于与该项目直接相关的初步研究或我们以前使用类似方法的经验。在第一个目标中，我们将使用化学信息学来鉴定约100种命中化合物，这些化合物可能是C3 b上四个靶位点之一的结合剂，在AP C3前转化酶形成中具有已知的作用。然后，在第二个目标中，我们将使用已建立的生物化学和功能工具来验证约20个既结合C3 b又抑制AP活性的候选物。在最后的目标，我们将使用结构比较，以确定药效团在这些验证的候选人，并进行有限的合成扩展，我们最有前途的~ 5化合物系列。在这个目标的结论，我们将确定一个单一的，无毒的化合物，将作为我们的AP C3前转化酶组装的主要抑制剂。因此，这项工作将为未来开发新的补体靶向抗炎疗法奠定基础。

DESCRIPTION (provided by applicant): Although complement serves as a pillar of the innate immune system, inappropriate or uncontrolled levels of complement activation are a major contributor to a rapidly growing list of human inflammatory diseases. Yet even though therapeutic manipulation of the complement response would be tremendously important in the clinic, only a limited panel of FDA approved drugs and indications exist for specifically targeting an active component within the complement system. A major factor underlying this dearth of complement-targeted therapeutics is the large size of the proteins and complex nature of the molecular recognition events which underlie complement activity. This has made it very challenging for scientists to identify which specific points are most susceptible for therapeutic intervention. By contrast, the bacterial pathogen Staphylococcus aureus deploys an array of proteins that have been naturally selected and exquisitely optimized during the course of host/pathogen co-evolution to efficiently block fundamental events within the complement cascade - in particular formation of the multi-subunit AP C3 convertase that drives amplification of the complement response. As a consequence, molecules which mimic the activities of staphylococcal virulence proteins hold promise for complement-directed, anti-inflammatory therapeutics. We recently investigated the potential of using novel cheminformatic tools for identifying small molecules that bind the same C3b site as the SCIN family of S. aureus complement inhibitors. Although done on a pilot scale, this work strongly suggested that in silico methods are a viable means of screening for new chemotypes of drug-like compounds that specifically target functionally significant sites on C3b. In this investigation, our goal is to aply the same cheminformatic methods to screen a highly elaborated (~20 million) compound library and to identify small molecules that bind C3b sites with known roles in the initial step of AP C3 convertase formation. This step, which generates a structure known as the AP C3 pro-convertase, is the same point in the pathway that is disrupted by multiple families of secreted S. aureus complement inhibitors (including SCINs). Thus, we believe that formation of the AP C3 pro-convertase is a biologically validated target for pharmacological intervention in the complement-mediated inflammatory response. The research plan described in this application consists of three distinct specific aims. Each aim has a defined outcome that is based upon either preliminary studies directly relevant to this project or our previous experience in using similar methodologies. In the first aim, we will use cheminformatics to identify ~100 hit compounds that are likely binders at one of four target sites on C3b with known roles in AP C3 pro-convertase formation. Then, in the second aim, we will use established biochemical and functional tools to validate ~20 candidates that both bind C3b and inhibit AP activity. In the fina aim, we will use structural comparisons to identify the pharmacophores in these validated candidates and conduct a limited synthetic expansion of our most promising ~ 5 compound series. At the conclusion of this aim, we will have identified a single, non-toxic compound that will serve as our lead inhibitor of AP C3 pro-convertase assembly. As a consequence, this work will lay the foundation for future development of new classes of complement-targeted anti-inflammatory therapeutics.