Characterization of small molecules that lower mutant huntingtin protein as potential therapeutics for Huntington’s disease

摘要 亨廷顿病 (HD) 是一种常染色体显性遗传、进行性、致命性神经退行性疾病， 影响全球 200,000 人。尽管该基因的发现已超过 25 年，且已有超过 150 临床试验表明，HD目前还没有有效的治疗方法。任何减缓、停止或 预防疾病对患者及其家人产生重大影响。 HD是扩容造成的 亨廷顿基因 (HTT) 中的 CAG 重复序列，导致亨廷顿蛋白中谷氨酰胺的延伸 蛋白质。正常亨廷顿蛋白 (HTT) 对于整个身体和大脑调节细胞生理至关重要 包括突触传递和神经保护、细胞分裂和分化、基因转录和 DNA损伤反应。在 HD 患者中，扩展的多聚谷氨酰胺束会导致突变 HTT (mHTT) 折叠异常，导致异常的翻译后修饰和裂解产生有毒的 mHTT 碎片。 N 端 mHTT 片段形成寡聚物，与许多细胞蛋白相互作用，破坏 细胞功能，导致 mHTT 水平增加并引起 mHTT 包涵体。大量神经元 纹状体中棘神经元 (MSN) 和大脑皮层发生功能障碍和死亡。实验性的 降低 mHTT 的手术可以逆转 HD 动物模型中的疾病症状。然而，临床 这种作用机制的翻译已经停滞，部分假设是由于非选择性降低 基本 HTT 和 mHTT。此外，一些处于临床试验阶段的候选药物针对的是 专门针对大脑，使用需要侵入性输送系统的治疗方式，而忽略身体的其他部位 未经治疗。因此，一种口服、全身分布、脑渗透的治疗方法可以选择性地 消除有毒的 mHTT，同时保留 HTT 的功能形式以支持正常生理机能可以提供 对所有 HD 患者有效的治疗。通过应用其筛选方面的专业知识，Origami Therapeutics (OT) 已 确定了一种以 OR1-113 为代表的化学支架，它可以防止 mHTT 聚集，并选择性地降低 已证实，通过自噬途径增强降解，从而提高基于细胞的检测中的 mHTT 水平 在 HD 患者来源的成纤维细胞、人 HD iPSC 来源的中型多棘神经元以及体内皮质和 HD YAC128 小鼠模型的纹状体。 ORI-113 的十二种类似物已被设计。功效 OR1-113 和 12 类似物的药物特性将在 HD 患者 iPSC 衍生的 MSN 中进行比较 体外吸收、分布、代谢和排泄研究将提供有关代谢的见解 以及药物化合物的潜在相互作用（目标 1）。药代动力学 (PK) 和脑暴露曲线 从目标 1 中选择的四种先导化合物将在小鼠中进行口服利用度测定（目标 2）。前两名 排名领先的药物将在 YAC128 小鼠中进行联合 PK/药效学和安全性研究中进行评估 管理（目标 3）。这些研究将确定一种主要的治疗药物候选物，该候选药物将进入 在开始临床测试之前需要进行研究性新药应用研究。

SUMMARY Huntington’s disease (HD) is an autosomal dominant, progressive and fatal neurodegenerative disease that effects 200,000 people worldwide. Despite discovery of the gene more than 25 years ago and more than 150 clinical trials, there is still no effective treatment for HD. The development of any therapy that slows, halts, or prevents disease would have a major impact on the patients and their families. HD is caused by the expansion of a CAG repeat in the huntingtin gene (HTT), resulting in an expanded stretch of glutamines in the huntingtin protein. Normal huntingtin protein (HTT) is essential throughout the body and brain to regulate cell physiology including synaptic transmission and neuroprotection, cell division and differentiation, gene transcription and the DNA damage response. In patients with HD, the expanded polyglutamine tract causes mutant HTT (mHTT) to fold abnormally, resulting in aberrant post-translational modifications and cleavage to generate toxic mHTT fragments. The N-terminal mHTT fragments form oligomers that interact with many cellular proteins, disrupting cell function, resulting in increased levels of mHTT and causing mHTT inclusions. Substantial neuronal dysfunction and death occur in striatal medium spiny neurons (MSNs) and the cerebral cortex. Experimental procedures that lower mHTT have reversed disease symptoms in animal models of HD. However, clinical translation of this mechanism of action has stalled and is, in part, hypothesized to be due to nonselective lowering of both the essential HTT as well as mHTT. In addition, some of the drug candidates in clinical trials target the brain exclusively, use therapeutic modalities that require invasive delivery systems and leave the rest of the body untreated. Therefore, an orally delivered, systemically distributed, brain-penetrant therapeutic that selectively eliminates toxic mHTT while sparing the functional forms of HTT to support normal physiology could offer an effective treatment for all HD patients. By applying its expertise in screening, Origami Therapeutics (OT) has identified a chemical scaffold, represented by OR1-113, that prevents mHTT aggregation, and selectively lowers mHTT levels in cell-based assays by enhancing degradation through an autophagy pathway as demonstrated in HD patient-derived fibroblasts, human HD iPSC-derived medium spiny neurons and in vivo in the cortex and striatum of the YAC128 mouse model of HD. Twelve analogues of ORI-113 have been designed. The efficacy and drug-like properties of OR1-113 and 12 analogues will be compared in HD patient iPSC-derived MSNs and in vitro absorption, distribution, metabolism, and excretion studies will provide insight regarding the metabolism and potential interactions of the drug compounds (Aim 1). Pharmacokinetic (PK) and brain exposure profiles of four lead compounds selected from Aim 1 will be determined in mice for oral availability (Aim 2). The top two ranked leads will be evaluated in a combined PK/Pharmacodynamic and safety study in YAC128 mice with oral administration (Aim 3). These studies will identify a lead therapeutic drug candidate that will move into Investigational New Drug Application studies that are required prior to initiation of clinical testing.