Immunoproteasome inhibitors for the treatment of Alzheimer’s disease

项目摘要 随着迄今为止几乎所有的AD药物临床试验的失败， 候选人已经成为带来有效的AD疗法的必要条件。一个主要障碍是缺乏 有希望的新药物靶点与导致淀粉样蛋白β（Aβ）和tau蛋白积聚的事件无关， 蛋白我们最近报道了靶向免疫蛋白酶体（iP）的线性肽环氧酮， 20 S组成型蛋白酶体（cP）的诱导型变体可能代表一类新的AD药物， 改善认知缺陷，独立于Aβ或tau积累。在显示出有希望的功效的同时， 然而，目前这些线性肽环氧酮用于AD的临床应用的前景似乎有限， 由于具有较差的脑可及性、体内代谢不稳定性和短循环时间的潜在问题 （主要归因于ABCB 1介导的药物在BBB的流出和肽酶的酶水解， 环氧化物水解酶）。然而，肽环氧酮家族（“具有C-末端α′，β′-环氧酮的短肽 Warhead“）仍然是有吸引力的候选药物，考虑到它们的药理学优点， 已证实的蛋白酶体靶向特异性和临床长期安全性。 我们目前的研究结果表明，一些含有大环的肽环氧酮家族成员具有 抵抗ABCB 1介导的外排的能力和上级其线性对应物的代谢稳定性，以及 可能成为AD患者有意义的新治疗方法。我们在此应用程序中的目标是识别 并表征最适合于体内脑iP抑制的这些大环化合物之一， 药物开发的下一阶段。为此，在aim 1中，我们将制备当前几组有前途的大环化合物， 具有不同结构特征的肽环氧酮，显示出相当的靶向抑制和生物学活性， 体外和细胞中的活性以克为单位。在目标2中，我们将表征每个大环化合物的体内性质， 肽环氧酮来鉴定先导候选药物。在目标3中，我们将验证体内功效和所提出的 先导候选药物的作用机制[iP抑制→（NLRP 3炎性小体）→抑制 小胶质细胞IL-1α释放→阻断星形胶质细胞转化（转化为A1亚型）→神经元存活]，使用两种 AD小鼠模型（APP/PS1和PS19 tau转基因小鼠）。完成建议的研究后，我们将 确定了一种具有IND使能研究和新型作用模式的最佳属性的主要候选药物。这些 通过检查以前未开发的有效性，预计结果将产生重要的积极影响。 iP靶向方法用于AD治疗，并可能为AD药物发现提供新的方向。

Project Summary With the failure of nearly all clinical trials for AD drugs in the pipeline to date, identification of a new class of drug candidates has become imperative to bring about effective AD therapies. A major obstacle is the lack of promising new drug targets unrelated to the events leading to the accumulation of the amyloid-beta (Aβ) and tau- protein. We recently reported that linear peptide epoxyketones targeting the immunoproteasome (iP), an inducible variant of the 20S constitutive proteasome (cP), may represent a new class of AD drugs that can ameliorate cognitive deficits, independently of Aβ or tau accumulation. While displaying promising efficacy, however, the prospect of these linear peptide epoxyketones for clinical use in AD appears limited at this time, due to potential issues of having a poor brain accessibility, in vivo metabolic instability, and short circulation time (largely attributable to the ABCB1-mediated drug efflux at the BBB and enzymatic hydrolysis by peptidases and epoxide hydrolases). Yet, the family of peptide epoxyketones (‘short peptides with C-terminal α′,β′-epoxyketone warhead’) remain attractive drug candidates considering their pharmacological advantages conferred by their proven target specificity for the proteasomes and long-term safety in the clinic. Our current findings reveal that some of the peptide epoxyketone family members containing a macrocycle have the ability to resist the ABCB1-mediated efflux and metabolic stability superior to their linear counterparts, and the potential to be a meaningful new treatment for patients with AD. Our objective in this application is to identify and characterize one of these macrocyclic compounds best suited for brain iP inhibition in vivo and proceed to the next phase of drug development. To do this, in aim 1 we will prepare the current sets of promising macrocyclic peptide epoxyketones with different structural features that displayed comparable target inhibition and biological activity in vitro and in cellulo on a gram scale. In aim 2, we will characterize in vivo properties of each macrocyclic peptide epoxyketone to identify a lead drug candidate. In aim 3, we will verify in vivo efficacy and the proposed mechanism of action of the lead drug candidate [iP inhibition → (NLRP3 inflammasome) → suppression of microglial IL-1α release → blockade of astrocytes transformation (to A1 subtype) → neuronal survival] using two mouse models of AD (APP/PS1 and PS19 tau transgenic mice). By completing the proposed study, we will have identified a lead candidate with the best attributes for IND enabling studies and novel mode of action. These results are expected to have an important positive impact by examining the validity of the previously untapped iP-targeting approach for AD therapy and potentially offering a new direction for AD drug discovery.