A Triazolotriazine-Based Dual GSK-3β/CK-1δ Ligand as a Potential Neuroprotective Agent Presenting Two Different Mechanisms of Enzymatic Inhibition

Glycogen synthase kinase 3 beta (GSK-3 beta) and casein kinase 1 delta (CK-1 delta) are emerging targets for the treatment of neuroinflammatory disorders, including Parkinson's disease. An inhibitor able to target these two kinases was developed by docking-based design. Compound 12, 3-(7-amino-5-(cyclohexylamino)-[1,2,4]triazolo[1,5-a][1,3,5]triazin-2-yl)-2-cyanoacrylamide, showed combined inhibitory activity against GSK-3 beta and CK-1 delta [IC50(GSK-3 beta)=0.17 mu m; IC50(CK-1 delta)=0.68 mu m]. In particular, classical ATP competition was observed against CK-1 delta, and a co-crystal of compound 12 inside GSK-3 beta confirmed a covalent interaction between the cyanoacrylamide warhead and Cys199, which could help in the development of more potent covalent inhibitors of GSK-3 beta. Preliminary studies on in vitro models of Parkinson's disease revealed that compound 12 is not cytotoxic and shows neuroprotective activity. These results encourage further investigations to validate GSK-3 beta/CK-1 delta inhibition as a possible new strategy to treat neuroinflammatory/degenerative diseases.