Targeting Hsp90 in cryptococcal fungal pathogenesis

摘要/摘要 病原微生物固有和获得性耐药性对人类健康构成严重威胁 在世界范围内造成了巨大的经济后果。真菌病原体是一个特别的挑战，因为 它们是真核生物，与它们感染的人类宿主有许多相同的生物学过程。其中 最有问题的真菌病原体是隐球菌，每年导致超过18万人死亡 在全球各地。隐球菌性脑膜炎是该病的主要临床表现，死亡率为100%。 如果不治疗，费率。即使有最好的治疗方法，死亡率仍然很高，因为药物的数量 在真菌中有不同靶点的类别非常有限，目前抗真菌药物的有效性是 受到剂量限制的寄主毒性或频繁出现高级别抗药性的影响。新的，非- 迫切需要治疗干预的交叉反应靶点。 在NIAID先前的支持下进行的工作中，我们已经证明了靶向分子伴侣Hsp90 在隐球菌和其他真菌中提供了一种强大的策略，以增强抗真菌药物的疗效和 消除抗药性。许多小分子已经很好地证实了Hsp90的“可药性”。 将这种蛋白质用于治疗人类癌症。目前的抗真菌活性和毒性较差。 然而，现有的药物需要开发真菌选择性抑制剂，如本修订所建议的那样 重新提交。 为了追求真菌选择性的目标，我们的跨学科团队现在已经解决了药物的结构- 白色念珠菌和新生隐球菌热休克蛋白90的结合结构域 各州。这些化学结构研究确定了真菌在构象灵活性方面的特定差异 使我们能够设计、合成和表征一类新的真菌选择性抑制剂。现在, 利用我们用之前的资金开发的新的基于化学和结构的设计方法，我们 将利用我们在真菌化学和分子生物学(考恩)和药物化学方面的互补专业知识 (布朗)继续进行结构活性关系(SAR)研究，但现在增加了新的 开发了计算算法来产生具有广谱抗真菌活性的抑制剂。药效 单独和与标准抗真菌药物联合使用的化合物将在培养和小鼠身上进行测试 耐药的白色念珠菌和新生念珠菌。除了产生重要的基本见解外，我们的结果还包括 可能会在不久的将来影响侵袭性真菌感染的治疗，因为它为 以一种新的方式开发实际的抗真菌药物候选药物。

Summary/Abstract Intrinsic and acquired drug resistance of pathogenic microorganisms poses a grave threat to human health and has enormous economic consequences worldwide. Fungal pathogens present a particular challenge because they are eukaryotes and share many of the same biological processes as the human hosts they infect. Among the most problematic fungal pathogens are species of Cryptococcus, which cause over 180,000 deaths per year across the globe. Cryptococcal meningitis, the major clinical manifestation of the disease, has a 100% mortality rate if left untreated. Even with best available therapies, mortality rates remain high because the number of drug classes that have distinct targets in fungi is very limited and the usefulness of current antifungal drugs is compromised by either dose-limiting host toxicity or the frequent emergence of high-grade resistance. New, non- cross-reactive targets for therapeutic intervention are urgently needed. In work performed with prior support from NIAID, we have shown that targeting the molecular chaperone Hsp90 in Cryptococcus and other fungi provides a powerful strategy to enhance the efficacy of antifungal drugs and abrogate drug resistance. The “druggability” of Hsp90 has been well established by many small molecules targeting this protein for the treatment of human cancers. The poor antifungal activity and toxicity of currently available drugs, however, demand development of fungal-selective inhibitors as proposed in this revised resubmission. To pursue the goal of fungal selectivity, our interdisciplinary team has now solved the structure of the drug- binding domain of Candida albicans and Cryptococcus neoformans Hsp90, both in unbound and inhibitor-bound states. These chemo-structural studies identified fungal-specific differences in conformational flexibility that allowed us to design, synthesize and characterize fungal-selective inhibitors of a new chemical class. Now, leveraging the new chemistry and structure-based design approaches we developed with previous funding, we will use our complementary expertise in fungal chemical and molecular biology (Cowen) and medicinal chemistry (Brown) to continue pursuing structure activity relationship (SAR) studies, but now augmented by newly developed computational algorithms to generate inhibitors with broad-spectrum antifungal activity. The efficacy of compounds alone and in combination with a standard antifungal will be tested in culture and in mice against drug-resistant C. albicans and C. neoformans. In addition to generating important basic insights, our results are likely to impact the treatment of invasive fungal infections in the near future by providing promising leads for development of actual antifungal drug candidates that operate in a new way.