Identification of treatments for chemical threat agent seizures

摘要：本项目的总体目标是为有机磷(OP)抗胆碱酯酶抑制剂和GABAA受体拮抗剂所致的急性癫痫发作寻找新的、更有效的医学对策。通过预防或阻止急性癫痫发作，这些对策将改善暴露于这些致痫剂量的个人的存活率和长期结果。 我们选择了两种OP试剂二异丙基氟磷酸盐(DFP)和梭曼(0-Pinacolyl甲基磷酸盐；GD)和一种GABAA受体拮抗剂四亚甲基二磺胺(TETS)来代表这两大类化学威胁物质。梭曼是OP神经毒素化学战剂(“神经毒剂”)的代表，被列为《化学物质》的附表1物质。 1993年《武器公约》。虽然DFP的效力低于《化学武器公约》有毒化学品清单中的神经毒剂，但其效果几乎相同。作为一种易挥发的毒剂，它可能会在封闭区域内迅速传播，可能会造成许多人伤亡，因此是一种可信的威胁剂。TETS是GABAA受体拮抗剂惊厥剂的代表，是一种高度致命的毒素，已被用作 杀鼠剂，但现在在世界上大多数国家都被禁止。然而，TETS致死中毒的事件时有发生。在mg基础上，TETS的杀伤力等同于OP化学战剂。最近，我们有机会表征了TETS在小鼠和大鼠体内的惊厥活性，当TETS通过ip、iv、口服和脑室内途径给药时。作为这项工作的结果，我们开发了第一个动物模型，在其中评估TETS在暴露前和暴露后给药的潜在治疗方法。在这个项目中，给大鼠注射DFP和梭曼，给小鼠注射TETS诱导癫痫发作。这些动物在接触各种潜在的治疗剂之前或之后以不同的时间间隔进行治疗。 (或组合)以评估测试试剂预防或终止行为或脑电抽搐活动的能力。OP模型中的测试以循序渐进的方式进行，首先针对DFP癫痫，因为DFP具有减少的安全顾虑并且可以在常规实验室环境中使用，然后与梭曼一起进行， 这需要美国陆军化学防御医学研究所提供极端的安全预防措施。所有的试验剂都与安定进行了比较，安定是目前紧急治疗化学暴露癫痫的标准护理。如果在癫痫发作早期给药，安定可能是有效的，但如果在癫痫发作过程中晚些时候给药，则癫痫可能会复发，药物可能无效。在……里面 此外，安定还可以降低血压和呼吸。另一个令人担忧的问题是，安定在被肌注时会不稳定地被吸收。路线(与储存的喷油器系统一样，以备在大规模伤亡情况下使用)。我们正在寻找能改善上述任何一种责任的安定的药物(或组合)。我们已经确定了一系列潜在的治疗方法(Tier 1)，目前 已批准在美国销售，或有人类数据可用，因此可以快速部署。此外，核心B和项目3将开发新的潜在治疗方法，它们是新的分子实体(Tier 2)。显示出优于安定活性的治疗方法将在项目2中研究其缓解癫痫引起的脑损伤的能力。最后，为了推进最有希望的疗法，我们将 完成各种其他研究，包括配方开发和安全性、毒理学和ADME研究，与A和B岩芯一起进行，以帮助就进一步开发做出通过/不通过的决策。

Summary: The overall objective of this project is to identify new, more effective medical countermeasures for the acute seizures produced by organophosphate (OP) anticholinesterase inhibitor and GABAA receptor antagonist chemical threat agents. By preventing or stopping the acute seizures, these countermeasures will improve the survival and long-term outcome of individuals exposed to seizure-inducing doses of these agents. We have selected two OP agents diisopropylfluorophosphate (DFP) and soman (0-pinacolyl methylphosphonofluoridate; GD) and one GABAA receptor antagonist tetramethylenedisulfotetramine (TETS) to represent the two broad classes of chemical threat agents. Soman, a representative of the OP neurotoxin chemical warfare agents ("nerve agents"), is classified as a Schedule 1 substance under the Chemical Weapons Convention of 1993. DFP, while less potent than the nerve agents in the Chemical Weapons Convention toxic chemicals list, has nearly identical effects. As a volatile agent that could rapidly spread inside closed areas, it could cause many injuries and deaths and is therefore a credible threat agent. TETS, a representative of the GABAA receptor antagonist convulsants is a highly lethal toxin that has been used as a rodenticide but is now banned in most countries of the world. Nevertheless, lethal poisoning with TETS occur regularly. On a mg basis, TETS is equal in lethality to the OP chemical warfare agents. Recently, we have had the opportunity to characterize the convulsant activity of TETS in mice and rats when administered by the i.p., i.v., oral and intracerebroventricular routes. As a result of this work, we have developed the first animal model in which to evaluate potential treatments for TETS when administered before and after exposure. In this project, DFP and soman are administered to rats and TETS is administered to mice to induce seizures. The animals are treated before or at various intervals following exposure with various potential therapeutic agents (or combinations) to assess the ability of the test agent to prevent or terminate behavioral or electrographic seizure activity. Testing in the OP models occurs in a step-wise fashion, first against DFP seizures because DFP has reduced safety concerns and can be used in a regular laboratory environment, and then with soman, which requires extreme safety precautions available at the US Army Medical Research Institute of Chemical Defense. All test agents are compared with diazepam, the current standard of care for the emergency treatment of chemical exposure seizures. Diazepam may be effective if administered early in the course of seizures but seizures may recur and the drug may be inactive if administered later in the course of seizures. In addition, diazepam can depress blood pressure and respiration. A further concern is that diazepam is erratically absorbed when administered by the i.m. route (as with the injector systems stockpiled for use in mass casualty situations). We are seeking agents (or combinations) that improve upon diazepam with respect to any of these liabilities. We have identified a series of potential therapies (Tier 1) that are either currently approved for sale in the U.S. or for which human data is available and can therefore be rapidly deployed. In addition, novel potential therapies that are new molecular entities (Tier 2) will be developed in Core B and Project 3. Therapies that exhibit superior activity to diazepam will be studied in Project 2 for their ability to mitigate seizure-induced brain damage. Finally, in order to advance the most promising therapies, we will complete various additional studies, including formulation development and safety, toxicology and ADME studies in conjunction with Cores A and B, to assist in making go/no-go decisions regarding further development.