cGAS inhibitors for Alzheimer's disease treatment

摘要 阿尔茨海默病（Alzheimer's disease，AD）是老年痴呆症中最常见的一种。β淀粉样蛋白（Aβ）和tau蛋白病理学 和神经炎症是阿尔茨海默病的三个主要标志。绝大多数的药物发现 在过去的几十年里，人们的努力集中在靶向Aβ病理学，但在临床试验中没有一个是成功的。 虽然tau病理学，而不是Aβ病理学，已经出现在AD记忆衰退中发挥关键作用，但药物 靶向tau蛋白对神经元的直接作用也没有取得成功。引人注目的人类基因研究 将先天性免疫反应与发展迟发性AD的风险升高联系起来，支持靶向小胶质细胞， 大脑中的常驻免疫细胞，作为AD的下一代治疗方法。我们发现， 环GMP-AMP合酶（cGAS）-干扰素基因（STING）信号转导的刺激因子， tau介导的认知能力下降。cGAS（一种主要的胞质dsDNA传感器）的激活催化了 cGAMP，一种非常有效的STING激动剂，作为激活cGAS-STING途径的第二信使， 导致通过激活干扰素调节因子（IRF）产生抗病毒应答， 细胞因子和I型干扰素基因的表达。我们发现部分或完全基因cGAS消融 在PS19 Tau小鼠中保护免于tau介导的空间学习和记忆缺陷。此外，治疗 与cGAS的小分子抑制剂一起使用可降低干扰素应答，减少小胶质细胞增生，并保护 针对具有tau蛋白病的AD小鼠模型中的认知缺陷。我们假设cGAS活性抑制剂 将抑制神经炎症和适应不良的免疫反应，防止AD相关的缺陷。我们 提出开发小分子人cGAS（h-cGAS）抑制剂作为治疗AD的新型小胶质细胞调节剂。 在目标1中，我们将从两个已知的命中开始开发先导h-cGAS抑制剂，并确定这些抑制剂是否 抑制剂在无细胞和基于细胞的测定中有效调节cGAS-STING途径。我们希望能找出 通过hits扩增和合成>200个类似物获得新的hits。目标2侧重于优化类似物， cGAS抑制剂TDI-6570，其是一种领先的低纳摩尔有效小鼠cGAS（m-cGAS）抑制剂，并具有 h-cGAS活性降低10倍。我们将设计多达50个新的类似物。合成孔径雷达的结果，对接实验，并在- 将使用silico计算来最大化潜在客户的质量。目标1和目标2的完成将导致5导联 用于体内和功效研究的化合物。在目标3中，我们将确定h-cGAS抑制剂在小鼠中的PK和功效。 tau蛋白病的小鼠模型，以及在人干细胞衍生的小胶质细胞和脑类器官中的功效， tau蛋白病在拟议的5年研究结束时，我们预计将确定1-2种先导h-cGAS抑制剂作为工具， 化合物和原理证明，以进一步发展为治疗阿尔茨海默病的候选药物， 相关的神经系统疾病。

ABSTRACT Alzheimer's disease (AD) is the most common form of dementia in elderly. Amyloid-β (Aβ) and tau pathologies and neuroinflammation are three major hallmarks of Alzheimer's disease. Vast majority of the drug discovery efforts in the past decades have focused on targeting the Aβ pathology, but none are successful in Clinical Trials. While tau pathology, not the Aβ pathology, has emerged to play critical role in memory decline in AD, drugs targeting the direct effects of tau on neurons also have not met success either. Compelling human genetic studies link the innate immune responses to elevated risk of developing late-onset AD, supporting targeting microglia, resident immune cells in the brain, as the next-generation treatment for AD. We showed that a critical role of cyclic GMP-AMP synthase (cGAS)-Stimulator of interferon genes (STING) signaling in microglial toxicity and tau-mediated cognitive decline. Activation of cGAS, a major cytosolic dsDNA sensor, catalyzes production of cGAMP, an extremely potent STING agonist as the second messenger that activates cGAS-STING pathway, leading to a production of the antiviral responses through activation of interferon regulatory factors (IRFs) and expression of cytokine and type I interferon genes. We found that a partial or complete genetic cGAS ablation protected against the tau-mediated spatial learning and memory deficits in PS19 Tau mice. Moreover, treatment with a small molecule inhibitor of cGAS reduces interferon responses, diminished microgliosis, and protected against cognitive deficits in an AD mouse model with tauopathy. We hypothesize that inhibitors the cGAS activity will dampen neuroinflammation and maladaptive immune responses, protect against AD-related deficit. We propose to develop small molecule human cGAS (h-cGAS) inhibitors as novel microglial modulators to treat AD. In Aim 1, we will develop lead h-cGAS inhibitors starting with two known hits and determine whether these inhibitors effectively modulate the cGAS-STING pathway in cell-free and cell-based assays. We expect to identify new hits via hits expansion and synthesize >200 analogs. Aim 2 focuses on optimization of analogs a potent cGAS inhibitor, TDI-6570, which is a lead low nanomolar potent mouse cGAS (m-cGAS) inhibitor and possesses 10x less h-cGAS activity. We will design up to 50 new analogs. Results of SAR, docking experiments, and in- silico calculation will be used to maximize the lead quality. Completion of Aim 1 and Aim 2 will lead to 5 lead compounds for in vivo and efficacy studies. In Aim 3, we will establish PK and efficacy of h-cGAS inhibitors in mouse model of tauopathy, and efficacy in human stem cell-derived microglia and cerebral organoids with tauopathy. At the end of the proposed 5 years study, we anticipate identifying 1-2 lead h-cGAS inhibitors as tool compounds and a proof of principle to further advance as drug candidates to treat Alzheimer's disease and related neurological disorders.