Identification of a novel pyrrolo[2,3- <i>b</i> ]pyridine compound as a potent glycogen synthase kinase 3β inhibitor for treating Alzheimer’s disease

Herein, a novel pyrrolo[2,3-<i>b</i>]pyridine-based glycogen synthase kinase 3β (GSK-3β) inhibitor, <b>S01</b>, was rationally designed and synthesised to target Alzheimer's disease (AD). <b>S01</b> inhibited GSK-3β, with an IC₅₀ of 0.35 ± 0.06 nM, and had an acceptable kinase selectivity for 24 structurally similar kinases. Western blotting assays indicated that <b>S01</b> efficiently increased the expression of p-GSK-3β-Ser9 and decreased p-tau-Ser396 levels in a dose-dependent manner. In vitro cell experiments, <b>S01</b> showed low cytotoxicity to SH-SY5Y cells, significantly upregulated the expression of β-catenin and neurogenesis-related biomarkers, and effectively promoted the outgrowth of differentiated neuronal neurites. Moreover, <b>S01</b> substantially ameliorated dyskinesia in AlCl₃-induced zebrafish AD models at a concentration of 0.12 μM, which was more potent than Donepezil (8 μM) under identical conditions. Acute toxicity experiments further confirmed the safety of <b>S01</b> in vivo. Our findings suggested that <b>S01</b> is a prospective GSK-3β inhibitor and can be tested as a candidate for treating AD.