Alzheimer's disease and novel nanotherapeutics exclusively targeting extrasynaptic NMDA receptors

项目摘要 阿尔茨海默病（AD）是一种进行性神经退行性疾病， 冲击AD临床试验中的失败率仍在~ 99%，寻找能阻止的高效药物的目标 和/或逆转AD的过程至今仍然难以捉摸。这些失败的原因之一是多因素的 这使得识别用于有效治疗干预的“正确”靶标非常具有挑战性。 NMDA受体（NMDAR）是在AD患者中临床验证的仅有的两个靶点之一。 美金刚的治疗剂量，美金刚是FDA批准的用于治疗中度至中度 严重AD，被证明可以延迟AD进展12周，并抑制空间学习的中断 通过预防由细胞外紧张性谷氨酸水平升高触发的谷氨酸能兴奋性毒性 导致突触外NMDAR（eNMDAR）的激活。然而，对美金刚的作用的荟萃分析 显示美金刚产生适度的、短暂的和高度异质的临床反应。施用 较高浓度的美金刚胺或在AD早期不是一种选择，因为美金刚胺可能 引发严重的精神模拟副作用，与突触介导的正常大脑活动阻滞有关。 NMDAR（sNMDAR）。将精力集中在阻断eNMDAR而不是sNMDAR的药物上将避免副作用 与NMDAR拮抗剂相关，同时产生增强的疾病修饰神经保护疗法。 为了解决对eNMDAR的排他性拮抗剂的迫切需求，我们应用了合理的药物设计， 设计了一个足够大的纳米颗粒（AuM），可以从突触间隙中排除，因此， sNMDAR，但仍然足够小以有效地穿透脑组织，到达并阻断eNMDAR。我们 发现在几种情况下，独家eNMDAR拮抗剂提供比美金刚强得多的神经保护作用。 与神经元兴奋性毒性相关的模型，包括保护树突棘免受Aβ寡聚体的影响。 基于这些令人兴奋的结果，我们建议对我们的独家eNMDAR进行广泛的评估 拮抗剂AuM在两种互补AD模型中的应用：5X-FAD小鼠，AD相关淀粉样蛋白沉积模型，和 P301 S tau × ApoE 4纯合子敲入小鼠，tau蛋白病模型。我们将比较AuM处理的小鼠和 用于疾病相关读数和结果的媒介物处理的小鼠，分别针对每个模型定制，包括 行为（记忆/学习）、淀粉样蛋白斑块或tau蛋白缠结蓄积、小胶质细胞活化/功能、CSF 生物标志物和神经病理学。我们还建议评估鼻-脑递送AuM的可行性 目的是为我们的纳米管建立一个临床相关的途径。具体来说，我们将确定 直接脑内递送或鼻内施用后5XFAD小鼠中AuM分布的时程。 在这个项目中获得的数据将使我们能够制定有效的战略，以追求IND使能 用于治疗AD的eNMDAR的排他性拮抗剂的研究。

PROJECT SUMMARY Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with a devastating socioeconomic impact. The failure rate in AD clinical trials is still ~99%, and the goal of finding efficient drugs that can stop and/or reverse the course of AD remains elusive so far. One of the reasons for these failures is a multifactorial nature of AD which makes it is very challenging to identify the “right” target for efficient therapeutic intervention. NMDA receptors (NMDARs) represent one of just two targets that were clinically validated in AD patients. Therapeutic doses of memantine, an NMDAR antagonist approved by the FDA for treatment of moderate-to- severe AD, were shown to delay the AD progression for 12 weeks and inhibit disruption of spatial learning through prevention of glutamatergic excitotoxicity triggered by elevated extracellular tonic glutamate levels leading to activation of extrasynaptic NMDARs (eNMDARs). However, meta-analysis of the memantine’s effects shows that memantine produces modest, short-lived, and highly heterogeneous clinical response. Administering memantine at higher concentrations or during the earlier AD stages is not an option because memantine may trigger serious psychomimetic side effects associated with the block of normal brain activity mediated by synaptic NMDARs (sNMDARs). Focusing efforts on drugs that block eNMDARs but not sNMDARs will avoid side effects associated with NMDAR antagonists, while producing an enhanced disease-modifying neuroprotective therapy. To address the critical need for exclusive antagonists of eNMDARs, we applied the rational drug design and engineered a nanotherapeutic (AuM) that is sufficiently large to be excluded from the synaptic cleft, thus, sparing sNMDARs, but still small enough to efficiently penetrate the brain tissues, reaching and blocking eNMDARs. We found that exclusive eNMDAR antagonists provide much stronger neuroprotection than memantine in several models associated with glutamatergic excitotoxicity, including protection of dendritic spines from Aβ oligomers. Based upon these exciting results, we propose to conduct an extensive evaluation of our exclusive eNMDAR antagonist AuM in two complementary AD models: 5X-FAD mice, a model of AD-related amyloid deposition, and P301S tau × ApoE4 homozygous knock-in mice, a tauopathy model. We will compare AuM-treated mice to vehicle-treated mice for disease-relevant read-outs and outcomes, tailored respectively to each model, including behavior (memory/learning), accumulation of amyloid plaques or tau tangles, microglial activation/function, CSF biomarkers, and neuropathology. We also propose to evaluate the feasibility of nose-to-brain delivery of AuM with the goal of establishing a clinically relevant route for our nanotherapeutic. Specifically, we will determine the time course of AuM distribution in 5XFAD mice after either direct intra-brain delivery or intranasal administration. The data acquired during this project will allow us to develop the efficient strategy to pursuit of IND-enabling studies for exclusive antagonists of eNMDARs for treatment of AD.