Discovery of Small-Molecule Degraders for Alpha-Synuclein Aggregates

Alpha-synuclein (αSyn) species, especially the oligomers and fibers, are associated with multiple neurodegenerative diseases and cannot be directly targeted under the conventional pharmacological paradigm. Proteolysis-targeting chimera technology confers degradation of various “undruggable” targets; however, hardly any small-molecule degrader for αSyn aggregates has been reported yet. Herein, by using the probe molecule sery308 as a warhead, a series of small-molecule degraders for αSyn aggregates were designed and synthesized. Their degradation effects on αSyn aggregates were evaluated on a modified pre-formed fibril-seeding cell model. Compound 2b exhibited the highest degradation efficiency (DC50 = 7.51 ± 0.53 μM) with high selectivity. Mechanistic exploration revealed that both proteasomal and lysosomal pathways were involved in this kind of degradation. Moreover, the therapeutic effects of 2b were tested on SH-SY5Y (human neuroblastoma cell line) cells and Caenorhabditis elegans. Our results provided a new class of small-molecule candidates against synucleinopathies and broadened the substrate spectrum of PROTAC-based degraders.α-突触核蛋白（Alpha-synuclein, αSyn）聚集体，尤其是寡聚体与纤维聚集体，与多种神经退行性疾病密切相关，且在传统药理学范式下难以实现直接靶向干预。蛋白水解靶向嵌合体（Proteolysis-targeting chimera, PROTAC）技术可介导多种“不可成药”靶点的降解；然而目前尚未见针对αSyn聚集体的小分子降解剂相关报道。本文以探针分子sery308作为弹头结构，设计并合成了一系列针对αSyn聚集体的小分子降解剂。通过改良的预形成纤维播种细胞模型，评估了该系列降解剂对αSyn聚集体的降解活性。化合物2b展现出最高的降解效率（DC50 = 7.51 ± 0.53 μM），且具备优异的选择性。机制探究结果表明，蛋白酶体与溶酶体通路均参与了该类降解过程。此外，本文在人神经母细胞瘤细胞系SH-SY5Y以及秀丽隐杆线虫（Caenorhabditis elegans）模型中验证了2b的治疗效果。本研究为突触核蛋白病（synucleinopathies）提供了一类全新的小分子候选药物，同时拓展了PROTAC类降解剂的底物谱。