New sterol-binding targets and optimized EBP inhibitors for promoting remyelination

摘要 脱髓鞘疾病，包括多发性硬化症，其特征在于髓鞘生成的缺失， 中枢神经系统中的少突胶质细胞，并导致数百万患者的严重残疾。 MS的现有疗法专门调节免疫系统以防止额外的髓鞘损失; 没有再生疗法可用于补充丢失的少突胶质细胞和修复丢失的髓鞘。 多位研究人员已经使用小分子文库的高通量筛选来鉴定药物 在体外增加从少突胶质细胞祖细胞（OPCs）形成少突胶质细胞 并增强体内功能性髓鞘再生。一种这样的分子，FDA批准的抗组胺药 氯马斯汀，最近被证明可以提高MS患者的视神经传导速度， 神经炎，提供了第一个临床证据，表明小分子治疗可以增强髓鞘再生 在人类中枢神经系统中。 虽然这项试验为未来的髓鞘再生治疗提供了概念验证，但更清晰的是， 控制少突胶质细胞形成的最佳途径和靶点对于 未来的翻译工作。我们的多学科团队利用了神经胶质细胞的协同专业知识， 生物学、化学生物学和有机合成提供了令人信服的初步证据，现在 发表在《自然》和《细胞化学生物学》上，几乎所有的早髓鞘小分子都被鉴定出来， HTS通过抑制少突胶质细胞内的少量相邻酶来增强少突胶质细胞的形成。 胆固醇生物合成抑制这些酶会导致特定的，结构上- 相关的胆固醇前体（8，9-不饱和甾醇），其足以促进形成 的少突胶质细胞。基于质谱的甾醇分析已经证明了更多 包括氯马斯汀在内的三十多种早髓鞘形成小分子通过这种机制发挥作用。 这一应用提出了两个并行的目标。首先，我们试图了解8，9-不饱和甾醇 积累驱动少突胶质细胞的形成，包括确定最佳甾醇和阐明 目标1和目标2（目标1和目标2）。此外，我们的目标是优化第一选择和大脑- 渗透性EBP抑制剂，并验证该分子促进体内和人体髓鞘再生 体外髓鞘形成（Aim 3）。有机合成是整个应用过程中的关键技术， 能够合成新的8，9-不饱和甾醇（Aim 1），光亲和下拉试剂（Aim 2），以及我们最近公开的抑制EBP的先导分子CW 9009和 CW9956。这些研究将加速髓鞘再生治疗的新兴领域， 开发优化的小分子用于进一步的药物开发和鉴定新的药物靶点 这是8，9-不饱和甾醇增强少突胶质细胞作用的基础。

ABSTRACT Demyelinating diseases, including multiple sclerosis, are characterized by loss of myelin-producing oligodendrocytes in the central nervous system and cause severe disability for millions of patients. Existing therapies for MS exclusively modulate the immune system to prevent additional myelin loss; no regenerative therapies are available that replenish lost oligodendrocytes and repair lost myelin. Multiple researchers have used high-throughput screening of small-molecule libraries to identify drugs that increase the formation of oligodendrocytes from oligodendrocyte progenitor cells (OPCs) in vitro and enhance functional remyelination in vivo. One such molecule, the FDA-approved antihistamine clemastine, was recently shown to enhance optic nerve conduction velocity in MS patients with optic neuritis, providing the first clinical evidence that small molecule treatments can enhance remyelination in the human CNS. While this trial provides proof-of-concept for future remyelinating therapeutics, greater clarity around the optimal pathways and targets controlling oligodendrocyte formation is critical to the success of future translational efforts. Our multi-disciplinary team has leveraged synergistic expertise in glial biology, chemical biology, and organic synthesis to provide compelling preliminary evidence, now published in Nature and Cell Chemical Biology, that almost all promyelinating small molecules identified by HTS enhance oligodendrocyte formation by inhibiting a small number of adjacent enzymes within cholesterol biosynthesis. Inhibition of these enzymes causes accumulation of specific, structurally- related cholesterol precursors (8,9-unsaturated sterols) which are sufficient to enhance the formation of oligodendrocytes from OPCs. Mass spectrometry-based sterol profiling has demonstrated more than three dozen promyelinating small molecules function by this mechanism, including clemastine. This application advances two parallel goals. First, we seek to understand how 8,9-unsaturated sterol accumulation drives oligodendrocyte formation, including defining the optimal sterols and elucidating their cellular target (Aims 1 and 2). Additionally, we aim to optimize the first selective and brain- penetrant EBP inhibitor and to validate that this molecule promotes remyelination in vivo and human myelin formation in vitro (Aim 3). Organic synthesis is a key technique throughout the application, enabling the synthesis of novel 8,9-unsaturated sterols (Aim 1), photoaffinity pulldown reagents (Aim 2), and novel derivatives of our recently-published EBP-inhibiting lead molecules CW9009 and CW9956. Together these studies will accelerate the emerging field of remyelinating therapeutics by developing optimized small molecules for further drug development and identifying novel drug targets that underlie the oligodendrocyte-enhancing effects of 8,9-unsaturated sterols.