Potent glycogen synthase kinase-3 (GSK-3) inhibitor (Ki = 0.6 nM for GSK-3α and GSK-3β). Displays high selectivity (> 50-fold) for GSK-3 over a panel of other kinases tested, including CDK family members. Decreases phosphorylation of microtubule-associated protein Tau in vitro; protects rat primary cortical neurons against β amyloid and glutamate challenge. Brain penetrant. Purity 99%. MW (observed): 362.31