Preclinical Evaluation of a Novel Hsp90 inhibitor in Mutant Tau Mice

描述（由申请人提供）：MAPT（微管相关蛋白tau）基因的遗传突变导致tau蛋白的病理和神经元内聚集，导致额颞叶痴呆（FTD）。对于这些常染色体tau病和其他神经系统疾病（如阿尔茨海默病（AD）和帕金森病（PD））患者来说，开发治疗错误折叠和异常加工（即过度磷酸化）tau物种的药物是必要的。这些疾病存在异常tau积聚，如阿尔茨海默病（AD）和帕金森病（PD）。在热休克刺激后诱导的分子伴侣引导错误折叠的蛋白质重新折叠和/或靶向蛋白酶体进行降解。热休克蛋白90 （HSP90）抑制剂，如格尔达霉素（GA）及其衍生物（17-烯丙基氨基-17-去甲氧基格尔达霉素，17-AAG）可以从药理学上调节伴侣蛋白水平，最近被认为与癌症治疗有关；赞助NCI， II期)和神经退行性疾病小鼠模型。事实上，Waza及其同事最近表明，通过减少单体和聚集突变雄激素受体的数量，系统给药17-AAG可以显著改善脊髓和球性肌萎缩转基因小鼠模型的运动障碍和寿命，而没有可检测到的毒性。这项研究表明，Hsp90抑制剂可以长期（20周）给药，并且耐受性良好。在一种新的细胞内Western检测中筛选了一小组新型HSP90抑制剂，该检测允许直接在细胞内定量天然和异常tau蛋白物种，我们发现了一种有效的，血脑屏障可渗透的HSP90抑制剂（EC102），可显着减少体外异常tau蛋白物种。此外，我们发现，人AD脑组织中受影响区域的Hsp90对这种新型抑制剂的纳摩尔结合亲和力明显低于肿瘤细胞，而未受影响区域的Hsp90对这种新型抑制剂的纳摩尔结合亲和力与正常细胞相当。这首次表明，在神经退行性疾病（本例中为AD）中，异常蛋白逐渐积聚的神经元中，Hsp90参与了这些蛋白的活性陪伴和稳定，并采用了一种新的高亲和力状态。因此，这些研究为使用Hsp90抑制剂增强AD中Hsp90介导的磷酸化tau降解提供了令人信服的证据。因此，我们提出用这种化合物治疗可以延缓由四环素操作符（rTg4510）驱动的人类tau （P301L）突变形式的小鼠的病理进展和恢复记忆丧失。

DESCRIPTION (provided by applicant): Hereditary mutations within the MAPT (microtubule-associated protein tau) gene result in the pathologic and intra-neuronal aggregation of the tau protein that leads to frontotemporal dementia (FTD). The development of therapeutics for misfolded and abnormally processed (i.e. hyper-phosphorylated) tau species is necessary for sufferers of these autosomal tauopathic disorders and other neurological disorders which present with abnormal tau accumulation such as Alzheimer's disease (AD) and Parkinson's disease (PD). Molecular chaperones that are induced following a heat shock stimulus direct either the refolding of misfolded proteins and/or their targeting to the proteasome for degradation. Heat shock protein 90 (HSP90) inhibitors such as geldanamycin (GA) and its derivatives (17-allylamino-17-demethoxygeldanamycin; 17-AAG) can pharmacologically modulate chaperone levels and have recently been implicated for the treatment of cancer; sponsor NCI, Phase II) and mouse models of neurodegenerative disorders. In fact, Waza and colleagues recently showed that systemic administration of 17-AAG can markedly ameliorate motor impairments and life span in the spinal and bulbar muscular atrophy transgenic mouse model without detectable toxicity, by reducing amounts of monomeric and aggregated mutant androgen receptor. This study illustrates that Hsp90 inhibitors can be administrated chronically (20 weeks) and is well-tolerated. After screening a small panel of novel HSP90 inhibitors in a novel In-Cell Western assay that allows for direct intracellular quantitation of native and aberrant tau protein species, we identified a potent, blood brain barrier permeable HSP90 inhibitor (EC102) that significantly reduces abnormal tau species in vitro. In addition, we found that affected regions from human AD brain tissue have a significantly lower nanomolar binding affinity of Hsp90 for this novel inhibitor similar to tumor cells, while micromolar affinity was demonstrated in unaffected regions, comparable to normal cells. This suggests for the first time that in neurons, which progressively accumulate abnormal proteins in neurodegenerative disorders, and in this case AD, Hsp90 becomes engaged in active chaperoning and stabilization of these proteins and the Hsp90 adopts a novel high-affinity state. Thus these studies provide compelling evidence for the use of Hsp90 inhibitors to enhance Hsp90-mediated phospho-tau degradation in AD. We therefore propose that treatment with this compound may delay the progression of pathology and restore memory loss in mice that express a mutant form of human tau (P301L) driven by the tetracycline operator (rTg4510).