A potent GSK3β inhibitor with IC50 of 22 nM; prevents tau phosphorylation both in vitro and in vivo; also inhibits CDKs at higher concentrations, including Cdk1/cyclin B (IC50=180 nM), Cdk2/cyclin A (IC50~500 nM), Cdk2/cyclin E (IC50=250nM), Cdk4/cyclin D1 (IC50=3.3 uM) and Cdk5/p35 (IC50=100 nM); reversibly inhibits the proliferation of many cells types, arresting cycling in the G2/M phase.