Cell-permeable. A selective glycogen synthase kinase 3 (GSK-3) inhibitor (IC₅₀ = 104 nM). Inhibition is competitive with respect to ATP (Ki = 38nM). Exhibits specificity for GSK-3 over cdk2 and cdk5 (IC₅₀ values are > 100 μM) and over 26 other kinases. Inhibits β-amyloid-mediated neurodegeneration in hippocampal slices.