Small molecule inhibitors of ricin and shiga toxins

描述（由申请人提供）：蓖麻毒素是一种在蓖麻籽中发现的强效B类蛋白毒素。它的易于准备使其成为国内和国际恐怖分子最喜欢的特工。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已将蓖麻毒素小分子抑制剂的鉴定和生产作为其生物防御计划的重中之重。为了实现这一目标，我们的项目是由三个具有互补技能的实验室合作完成的，它们可以促进抑制剂的设计、合成和测试。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，它可以作为大型商业图书馆的现代计算机虚拟屏幕的模板。最有吸引力的候选人将在体外分析系统中进行评估。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， IC50为1 DM。此外，使用新开发的微板试验的高通量筛选将在哈佛NSRB设施进行。然后，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进行优化，并使用最先进的组合化学技术专门创建多样性库。我们希望将IC50值提高至少10到100倍，达到纳摩尔范围。我们提高抑制剂强度的第一个努力是在三个位置分散Z3911平台，创建一个小的衍生化合物库。提出了详细的综合策略，并作为从未知平台开发额外线索的方式的示例。在设计方案中，较强的体外抑制剂，如Z3911，将在Vero细胞试验中进行早期测试。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化合物的努力。有效的，无毒的，蓖麻毒素抑制剂将在动物挑战模型中进行评估，以最终改进化合物。我们的目标是创造蓖麻毒素（和同源志贺毒素）抑制剂，可以预防或减轻动物的毒性，并作为商业或政府机构开发真正解毒剂药物的基础。

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.