Targeting JNK3 for Alzheimer's Disease: Design and Synthesis of Novel Inhibitors with Aryl Group Diversity utilizing Wide Pocket

JNK3, a brain-specific stress-activated protein kinase, plays a critical role in Alzheimer's disease pathogenesis through phosphorylation of Tau and APP. This study aimed to develop selective JNK3 inhibitors based on a pyrazole scaffold, focusing on (E)-1-(2-aminopyrimidin-4-yl)-4-styryl-1H-pyrazole-3-carboxamide derivatives. Through systematic structural modifications and extensive SAR analysis, we identified compounds 24a and 26a as highly potent JNK3 inhibitors, with IC₅₀ values of 12 and 19 nM, respectively. Especially, 24a revealed its potent and selective inhibition of JNK3, coupled with inhibition of the GSK3α/β kinases involved in Tau phosphorylation. In vitro studies revealed significant neuroprotective effects against Aβ_1-42-induced toxicity in primary neuronal cells and western blot analyses confirmed the compounds' ability to mitigate Aβ_1-42-induced c-Jun and APP phosphorylation, suggesting a multi-faceted approach to neuroprotection. Docking studies validated the retention of optimal interactions within the JNK3 binding pocket. Importantly, BBB PAMPA assays and ADME predictions indicated favorable blood-brain barrier permeability and pharmacokinetic profiles for the lead compounds. These findings represent a significant advancement in the development of selective JNK3 inhibitors, providing a strong foundation for further preclinical development of potential Alzheimer's disease therapeutics.