Development of non-toxic amphotericin B derivatives targeting invasive fungal infections

1.项目摘要/摘要 侵袭性真菌感染(IFI)是越来越多的 免疫功能受损的患者，而成功的治疗是出了名的困难。领先的FDA批准 抗真菌类别受到临床疗效不足的限制，这通常是由于剂量限制的毒性， 新出现的耐药性、药物与药物的相互作用以及治疗监测的必要性。新型抗真菌药物 对广谱病原体的强大活性，对耐药性的最小敏感性，以及有限的副作用 效果是需要的。两性霉素B(Amb)表现出剂量依赖的杀伤力，具有杀菌作用，具有 异常广谱，没有抗药性发展的报道。然而，商业上的 现有形式的AMB，包括AmBisome®，既有急性毒性，也有慢性毒性，因此无法安全使用 高剂量。这种毒性阻碍了AMB的全部临床潜力的实现。我们的目标是开发一种 化学修饰的Amb衍生物具有广泛的强效杀菌活性，缺乏抗药性， 最重要的是，毒性有限。这将使临床医生能够安全地使用大剂量治疗方案 更有效地治疗IFI。推翻了半个世纪的先前想法，我们发现Amb主要杀死了这两个人 真菌和人类细胞分别通过简单地结合麦角甾醇和胆固醇。在这种洞察力的指引下，我们 最近设计了一种新的Amb衍生物C2‘epamB，它选择性地与麦角甾醇结合在胆固醇之上。 因此，C2‘epAmB对多种病原体具有良好的杀菌活性，且对人体无毒 原代肾上皮细胞(HRECs)、小鼠和大鼠在测试的最高剂量下。然而，C2的epAmB也 在效力和病原体范围方面有重要限制。我们实验室的早期研究发现 含有C16上尿素基序的AMB衍生物，显示出更强的抗真菌活性，但仍不能接受 毒物。在这个研究项目中，我们将结合C2‘epAmB中的消除毒性的C2’修饰和 在C16上对尿素进行增效修饰，以开发一类新的杂化多烯杀菌剂 既无毒又在根除IFI方面非常有效。一种具有代表性的混合衍生品，我们最近 合成的C2‘epAmBAU对一系列重要病原体具有优异的效力，最低限度 HRECs的毒性。在这些和许多其他令人鼓舞的初步成果的基础上，我们现在计划 合成了一类C2的表观氨基尿苷，并在最先进的生物物理中对它们进行了广泛的表征， 机制、抵抗力、有效性和毒性研究，以确定最有希望的候选者 新的“大剂量”临床范例，以更好地治疗IFI。为了实现所有这些目标，我们组建了一个 世界一流的多学科专家团队，从事化学合成、抗真菌开发、药代动力学、 分子真菌学和IFI的临床处理。在此计划的最后，我们将针对 使用一种潜在的变革性新的抗真菌药物进行的使能IND的研究。

1. Project Summary / Abstract Invasive fungal infections (IFI) are a leading cause of death in the growing number of immunocompromised patients, and successful therapy is notoriously difficult. Leading FDA-approved antifungal classes are limited by inadequate clinical efficacy, which is often due to dose-limiting toxicities, emerging resistance, drug-drug interactions, and the need for therapeutic monitoring. New antifungals with robust activity against a broad spectrum of pathogens, minimal susceptibility to resistance, and limited side effects are needed. Amphotericin B (AmB) demonstrates dose-dependent killing, is fungicidal, has exceptionally broad spectrum, and has no reported development of resistance. However, the commercially available forms of AmB, including AmBisome®, have both acute and chronic toxicities that preclude safe use at high doses. This toxicity hinders realization of the full clinical potential of AmB. Our goal is to develop a chemically modified AmB derivative with a broad spectrum of robust fungicidal activity, lack of resistance, and, most importantly, limited toxicity. This will enable clinicians to safely employ high-dose treatment protocols to more effectively treat IFI. Overturning half a century of prior thinking, we found that AmB primarily kills both fungal and human cells by simply binding ergosterol and cholesterol, respectively. Guided by this insight, we recently designed a new AmB derivative, C2’epiAmB, which selectively binds ergosterol over cholesterol. Accordingly, C2’epiAmB retains good fungicidal activity against many pathogens, and is non-toxic to human primary renal epithelial cells (hRECs), mice, and rats at the highest doses tested. However, C2’epiAmB also has important limitations with respect to potency and pathogen scope. Earlier studies from our labs identified AmB derivatives bearing urea motifs at C16 which show increased antifungal potency but retain unacceptable toxicities. In this research program, we will combine the toxicity-eliminating C2’ modification in C2’epiAmB with efficacy-promoting urea modifications at C16 to develop a new class of hybrid polyene fungicidal agents that are both non-toxic and highly effective in eradicating IFI. A representative hybrid derivative that we recently synthesized, C2'epiAmBAU, has excellent potency against a series of important pathogens and minimal toxicity in hRECs. Building on these and many other encouraging preliminary results, we now plan to synthesize a family of C2’epiAmBUreas and extensively characterize them in state-of-the-art biophysical, mechanistic, resistance, efficacy, and toxicity studies, to identify the most promising candidates for enabling a new ‘high-dose’ clinical paradigm for better treating IFI. To accomplish all these goals, we have assembled a world-class multidisciplinary team of experts in chemical synthesis, antifungal development, pharmacokinetics, molecular mycology, and the clinical management of IFI. At the end of this proposal, we will be positioned for IND-enabling studies with a potentially transformative new antifungal agent.