Broad-spectrum Antifolates for Treatment of Drug Resistant Bacillus anthracis

描述（由申请人提供）：吸入性炭疽是一种威胁生命的疾病，由炭疽芽孢杆菌孢子释放到环境中引起。这一事件的经济影响将达到数十亿美元，仅次于由此产生的发病率和死亡率数字。虽然已批准的抗生素可用于治疗炭疽，但它们代表了目前用于其他疾病的标准类别。炭疽芽胞杆菌存在对某些抗菌素的耐药菌株，利用目前的分子工具可以培育出对所有可用药物的耐药菌株。只有一种新的抗微生物药物处于后期开发阶段，可有效预防吸入性炭疽感染。本R01提案的目标是开发一种新的抗微生物药物组合，用于治疗吸入性炭疽，该组合将抑制一种关键的代谢酶，二氢叶酸还原酶（DHFR）。炭疽DHFR对这一靶点的唯一临床药物具有固有的耐药性。因此，如果多重耐药炭疽芽胞杆菌被秘密制造出来，DHFR可能不会改变，这些新的抗菌剂将对这些菌株有效。通过R21筛选，发现了几种新的亲本化合物，它们对细菌DHFR （ic50为46 ~ 100 nM）具有选择性抑制作用，而对人DHFR （ic50为50 ~ 2.5万nM）没有选择性抑制作用。该方法将涉及来自不同学科的科学家团队，包括生物化学、微生物学和结构生物学、硅技术、蛋白质化学、分子生物学、药物化学和动物模型。该申请是对RFA要求开发NIAID a、B和C类优先病原体治疗方法的具体响应。该应用程序将涉及以下里程碑：里程碑1：合成4个以上的母化合物，这些母化合物是根据晶体学工作模型和以前的研究设计的；里程碑2：提出25种建议的第一代化合物，使用硅药物设计方法；里程碑3：开始PK和MTD研究；里程碑4：从第一代衍生物中合成和分析8个选定的化合物；里程碑5：完成MTD/PK研究；里程碑6：评估第一代先导化合物对小鼠炭疽模型的疗效；里程碑7：确定1-3个先导化合物用于临床前开发。这种多学科的努力将涉及学术和私人拥有的研究机构参与一个全面的基于团队的计划，通过产品开发途径促进有前途的治疗方法的进步。与公共卫生相关的是发展一种治疗对策，将有效地对抗多药耐药的炭疽菌株。

DESCRIPTION (provided by applicant): Inhalation anthrax is a life-threatening disease that would result from the release of Bacillus anthracis spores into the environment. The economic impact of such an event, which would be secondary only to the resulting morbidity and mortality figures, would be in the billions. Although approved antibiotics are available for use against anthrax, they represent standard classes currently being used for other diseases. Resistant strains of B. anthracis exist for certain antimicrobials and development of resistant strains to all the available drugs is achievable with current molecular tools. There is only one new antimicrobial in late-stage development that is effective in preventing inhalation anthrax infections. The goal of this R01 proposal is to develop a new assemblage of antimicrobials for the treatment of inhalation anthrax that will inhibit a critical metabolic enzyme, dihydrofolate reductase (DHFR). The anthracis DHFR is inherently resistant to the only clinical drug for this target. Thus, if multiple-resistant B. anthracis were covertly created, DHFR would likely be unchanged and these new antimicrobials would be effective against those strains. Through an R21, several new parent compounds were identified that inhibit B. anthracis through selective activity against the bacterial DHFR (IC50s of 46-100 nM) but not human DHFR (IC50s > 25,000 nM). This approach will involve a team of scientists from diverse disciplines, including biochemistry, microbiology & structural biology, in silico technology, protein chemistry, molecular biology, medicinal chemistry, and animal models. The application is a specific response to a RFA request to develop therapeutics for NIAID Category A, B, and C priority pathogens. This application will involve the following Milestones: Milestone 1: Synthesize 4 more parent compounds designed from crystallographic working model and from previous studies; Milestone 2: Propose 25 suggested 1st generation compounds using in silico drug design methods; Milestone 3: Begin PK and MTD studies; Milestone 4: Synthesize and assay 8 selected compounds from 1st generation derivatives; Milestone 5: Complete MTD/PK studies; Milestone 6: Evaluate 1st generation lead compounds for efficacy in mouse anthrax model; Milestone 7: Identify 1-3 lead compounds for preclinical development. This multidisciplinary effort will involve both academic and privately owned research organizations participating in a comprehensive team-based plan that will facilitate the advancement of a promising therapeutic through the product development pathway. The public health relevance is the development of a therapeutic countermeasure that will be effective against multidrug-resistant strains of anthrax.