Small molecule inhibitors of ricin and shiga toxins

描述（由申请方提供）：蓖麻毒素是一种在蓖麻籽中发现的强效B类蛋白毒素。它易于制备，使其成为国内和国际恐怖分子最喜欢的代理人。由于针对毒素的疫苗接种不是保护普通民众的合理策略，NIAID已将鉴定和生产蓖麻毒素的小分子抑制剂作为其生物防御计划的首要任务。为了实现这一目标，我们的项目是三个实验室的合作努力，这些实验室具有促进抑制剂设计，合成和测试的互补技能。该项目将开始筛选现有的商业化合物，以确定蓖麻毒素抑制剂。由于蓖麻毒素的X射线结构是已知的，它可以作为一个现代计算机为基础的大型商业图书馆的虚拟屏幕的模板。最有吸引力的候选人将在体外分析系统中进行评估。对1000种化合物的初步筛选已经确定了三种抑制剂，其中一种称为Z3911，其IC 50为1 DM。此外，将在哈佛的NSRB机构使用新开发的微孔板试验进行高通量筛选。来自虚拟和物理筛选的抑制剂将在设计周期中使用基于结构的方法和使用最先进的组合化学专门创建的多样性文库进行优化。我们期望将IC 50值提高至少10至100倍至纳摩尔范围。我们提高抑制剂强度的第一个努力是在三个位置使Z3911平台多样化，创建一个小型衍生化合物库。一个详细的合成策略，并作为一个例子的方式，其中额外的线索将开发从未知的平台。在设计方案中，将在Vero细胞试验的早期测试合理强的体外抑制剂，如Z3911。这将使我们能够评估生物利用度和细胞毒性，并限制进一步设计有用的化合物。然后将在动物激发模型中评估有效、无毒的蓖麻毒素抑制剂，以最终精制化合物。我们的目标是创造蓖麻毒素（和同源滋贺毒素）抑制剂，可以预防或减轻动物毒性，并作为商业或政府机构开发真正解毒药物的基础。

DESCRIPTION (provided by applicant): Ricin is a potent class B protein toxin found in castor seeds. Its ease of preparation has made it a favorite agent for domestic and international terrorists. Since vaccination against the toxin is not a plausible strategy for protection of the general populace, NIAID has made identification and production of small molecule inhibitors of ricin a top priority in its program for Biodefense. Toward this goal, our project is a collaborative effort from three laboratories with complimentary skills that facilitate inhibitor design, synthesis and testing. The project will be initiated with screens of existing commercial compounds to identify ricin inhibitors. Since the x-ray structure of ricin is known, it can serve as a template for a modern computer based virtual screen of large commercial libraries. The most attractive candidates will be assessed in an in vitro assay system. An initial screen of 1000 compounds has already identified three inhibitors including one, called Z3911, with an IC50 of 1 DM. In addition, high throughput screens using a newly developed micro-plate assay will be conducted at the NSRB facilities at Harvard. Inhibitors from both virtual and physical screens will then be optimized in design cycles using both structure-base methods and specifically created diversity libraries using state of the art combinatorial chemistry. We expect to improve IC50 values at least 10 to 100 fold into the nanomolar range. Our first effort to improve inhibitor strength is to diversify the Z3911 platform at three positions, creating a small library of derivative compounds. A detailed synthetic strategy is presented, and serves as an example for the manner in which additional leads will be developed from as yet unknown platforms. In the design scheme, reasonably strong in vitro inhibitors, like Z3911, will be tested early on in a Vero cell assay. This will allow us to assess bioavailability, and cell toxicity, and to restrain further design efforts towards useful compounds. Potent, non-toxic, ricin inhibitors will then be assessed in an animal challenge model for the final refinement of compounds. Our goal is create ricin (and homologous shiga toxin) inhibitors that can prevent, or alleviate toxicity in animals and serve as the basis for development, by commercial or government agencies, of true antidote drugs.