Development and Evaluation of Purine and Coumarin Based Hsp90 Inhibitors

描述(申请人提供)：90 kDa热休克蛋白被证明是非同寻常的癌症化疗靶点，这一事实证明，目前有20多项临床试验正在进行中。不幸的是，所有这些试验都是基于N-末端抑制剂，主要是格尔达霉素衍生的，这些化合物表现出严重的配方、程序和剂量困难，因为这些化合物在诱导客户蛋白质降解的同时诱导HSP。Neck和他的同事之前的研究确定Hsp90含有一个C-末端的ATP结合位点，它与香豆素抗生素竞争结合而不是ATP。与N末端抑制剂一样，C末端结合域的抑制剂也会导致肿瘤细胞生长和增殖所需的依赖于Hsp90的客户蛋白的降解。香豆素抗生素的一个主要缺点是它们与Hsp90结合很弱(IC50约为700微摩尔)；然而，我们小组最近的研究导致化合物的活性是这些天然产物的1000倍。通过SAR研究，我们已经能够确定对Hsp90抑制很重要的功能，并学会了如何以以前没有意识到的方式调节Hsp90。因此，我们开发了在低浓度下诱导HSP的化合物，使变性蛋白重新折叠，作为治疗各种神经退行性疾病的新方法。相反，我们已经构建了在不诱导HSP的情况下抑制HSP90的分子，因此提供了一种机制，通过该机制可以绕过临床上观察到的N末端抑制剂的困难。在这一应用中，我们建议进一步开发基于我实验室开发的嘌呤和CoMFA模型的抗肿瘤药物，该模型将有助于构建更有效和更易溶的Hsp90 C末端结合位点的抑制剂。除了我们非凡的体内初步研究外，还建议在更多的体内癌症模型中进一步研究最活跃的化合物。作为这些研究的结果，我们相信我们可以提供一个新的平台，通过调节Hsp90蛋白折叠机制来为治疗癌症的新药提供基础或实现。与公共健康相关：这项提案的目标是通过靶向负责折叠多种致癌酶的蛋白质(Hsp90)来攻击这些酶，因为所有蛋白质都必须折叠才能变得活跃。尽管针对Hsp90的化合物的临床试验正在进行中，但它们表现出的有害特性被证明是难以克服的。我们已经确定了不表现出这些有害特性的分子，并已被证明在癌症的初步动物模型中是例外的。我们计划继续开发这些药物。

DESCRIPTION (provided by applicant): The 90 kDa heat shock proteins are proving to be extraordinary cancer chemotherapeutic targets as evidenced by the fact that more than 20 clinical trials are currently in progress. Unfortunately, all of these trials are based upon N-terminal inhibitors, primarily geldanamycin- derived, which exhibit serious formulation, scheduling and dosing difficulties as these compounds induce Hsp's at the same concentration they induce client protein degradation. Previous studies by Neckers and coworkers determined that Hsp90 contains a C-terminal ATP binding site that bound coumarin antibiotics competitively versus ATP. Like N-terminal inhibitors, inhibitors of the C-terminal binding domain also cause the degradation of Hsp90-dependent client proteins required for tumor cell growth and proliferation. A major drawback of the coumarin antibiotics is that they bind weakly to Hsp90 (IC50 approximately 700 micromolar); however, recent studies by our group have led to compounds ~1000 fold more active than these natural products. Through SAR studies we have been able to identify functionalities important for Hsp90 inhibition and have learned how to modulate Hsp90 in ways not previously realized. Thus, we have developed compounds that induce Hsp's at low concentrations that refold denatured proteins as a new method to treat various neurodegenerative diseases. In contrast, we have constructed molecules that inhibit Hsp90 without inducing Hsp's, and therefore provide a mechanism by which to bypass difficulties observed with N-terminal inhibitors in the clinic. In this application we propose to further develop the anti-tumor agents based on a purine and CoMFA model developed in my laboratory that will aid in the construction of more efficacious and soluble inhibitors of the Hsp90 C-terminal binding site. In addition to our extraordinary preliminary in vivo studies, it is proposed to further investigate the most active compounds in additional in vivo models of cancer. As a consequence of these studies, we believe we can provide a new platform for which new drugs can be based or realized for the treatment of cancer via modulation of the Hsp90 protein folding machinery. PUBLIC HEALTH RELEVANCE: The goal of this proposal is to attack multiple cancer-enabling enzymes by targeting a protein (Hsp90) that is responsible for folding them, as all proteins must be folded to become active. Although clinical trials are in progress for compounds that target Hsp90, they exhibit detrimental properties that are proving difficult to overcome. We have identified molecules that do not exhibit these deleterious properties and have proven to be exceptional in preliminary animal models of cancer. We plan to continue and develop these drugs.