ApoE4-targeted therapeutics that normalize SirT1

 描述(由申请人提供)：我们的研究首次将阿尔茨海默病的主要风险因素ApoE4与主要长寿决定因素sirtuins联系起来；并确定了针对这一新联系的第一种候选疗法。阿尔茨海默病(AD)目前在美国困扰着540多万人，估计每年给社会造成的损失超过2000亿美元。目前批准的治疗AD的药物只能提供短期的症状缓解，但不能改变疾病的进展。阿尔茨海默病(AD)的主要危险因素是载脂蛋白E(ApoE4)的epsilon-4(E4)等位基因，该基因存在于约三分之二的AD患者中。ApoE4等位基因(染色体19q13)增加了散发性和晚发性AD(LOAD)的风险。尽管十多年来人们知道ApoE4等位基因在疾病过程中起到了某种作用，但ApoE4相关AD风险的确切分子机制仍不清楚。我们的研究揭示了ApoE4介导的毒性的一种新机制，并揭示了一个关键的介质-SirT1-受ApoE4和ApoE3的不同影响。有趣的是，虽然ApoE3和ApoE4都与APP结合，但只有ApoE4与纳摩尔亲和力(Kd~80 nm)结合，并且只有ApoE4显著：(A)降低Sappa/A？；(B)减少SirT1的表达，导致SirT1水平显著降低，神经保护性SirT1与神经毒性SIRT2的比率显著降低；(C)触发tau和APP磷酸化；以及(D)诱导细胞程序性死亡。在我们的临床图书馆的初始屏幕中 我们已经确定了一种有希望的HIT(A03)，它是一种重新定位的候选药物，具有高度的脑渗透性，并逆转了SirT1水平的降低。作为这项建议的一部分，我们计划完成A03的临床前测试，并开发A03的新化学实体(NCE)类似物以供进一步开发。此外，通过筛选和“点击到领先”的优化，我们计划发现新的领先候选人进行进一步的测试。该提案的最终目标是为非GLP毒性测试提供1-2个候选对象。我们的数据支持这样一种假设，即神经元的连通性--受到包括Sappa：A？、SIRT2：SIRT1、APP：P-APP和tau：P-tau在内的关键介质比率的影响--被ApoE4程序性地改变。与临床核心中心和Gylys实验室的合作在该项目中非常重要，因为它将为ApoE基因分型患者的血浆和脑脊液样本提供SirT1水平的初步分析。这些数据将对未来ApoE4靶向药物的临床测试和SirT1作为MCI/AD潜在血浆生物标志物的开发非常有用。此外，计划将SirT1与血浆/脑脊液中受sirtuin/NFkB信号影响的其他生物标志物进行比较，这将有助于进一步阐明ApoE4在AD中的作用。该项目的总体主要目标是确定有效的、口服活性的、脑渗透的SirT1增强型领先候选药物，这些候选药物适合作为第一种针对ApoE4的针对AD的靶向SirT1疗法，适合于进一步的临床前IND开发，并开发必要的工具来确定目标参与和有效性。

 DESCRIPTION (provided by applicant): Our studies link for the first time the major risk factor for Alzheimer's disease - ApoE4 - with major longevity determinants, the Sirtuins; and identify the first candidate therapeutics that target this new link. Alzheimer's disease (AD) currently afflicts more than 5.4 million people in the US at an estimated cost to society of greater than $200 billion per year. The currently approved drugs for AD provide only short-term symptomatic relief but do not alter disease progression. The dominant risk factor for Alzheimer's disease (AD) is the epsilon-4 (e4) allele of apolipoprotein E (ApoE4), which is present in about two-thirds of AD patients. The ApoE4 allele (chromosomal locus 19q13) confers increased risk for sporadic and late-onset AD (LOAD). Despite over a decade of knowledge that the ApoE4 allele is somehow contributory to the disease process, the precise molecular mechanisms underlying ApoE4-associated AD risk remain unclear. Our studies shed light on a novel mechanism for ApoE4-mediated toxicity and revealed a key mediator - SirT1 - that is differentially affected by ApoE4 vs. ApoE3. Interestingly, while both ApoE3 and ApoE4 bind to APP, only ApoE4 associates with nanomolar affinity (Kd ~80nM), and only ApoE4 significantly: (a) reduces the ratio of sAPPa to Aß; (b) reduces SirT1 expression, resulting in a marked reduction of SirT1 levels and in the ratio of neuroprotective SirT1 to neurotoxic SirT2; (c) triggers tau and APP phosphorylation; and (d) induces programmed cell death. In our initial screen of a clinical library we have identified a promising hit (A03) that is a repurposing candidate, is highly brain permeable, and reverses the reduction of SirT1 levels. As part of this proposal we plan to complete the preclinical testing of A03 and develop new chemical entity (NCE) analogs of A03 for further development. In addition, through screening and "hit-to-lead" optimization we plan to discover new lead candidates for further testing. The eventual goal of the proposal is to provide 1-2 candidates for non-GLP toxicity testing. Our data support the hypothesis that neuronal connectivity - influenced by the ratios of critical mediators including sAPPa:Aß, SirT2:SirT1, APP:p-APP, and tau:p-tau - is programmatically altered by ApoE4. The collaboration with the Clinical Core and the Gylys lab is important in this project, as it would provide preliminary analysis of plasma and CSF samples from ApoE genotyped patients for levels of SirT1. Such data would be extremely useful for future development of ApoE4-targeted drug candidates to clinical testing and SirT1 as a potential plasma biomarker in MCI/AD. In addition, comparing SirT1 with other biomarkers in plasma/CSF that are affected by the sirtuin/NFkB signaling is planned and would help further elucidate the role of ApoE4 in AD. The overall primary objective of this project is to identify potent, orally active, brain permeable SirT1-enhancing lead candidates that are suitable for further preclinical IND development as the first ApoE4- targeted SirT1 therapeutics for AD and to development the tools necessary to ascertain target engagement and efficacy.