SB216763 is a potent, selective, and cell permeable glycogen synthase kinase-3 (GSK-3) inhibitor. It competes with ATP and potently inhibits the activity alpha and beta isozymes of GSK-3. GSK-3 is a serine/threonine protein kinase that is inhibited by an assortment of extracellular stimuli including insulin, growth factors, cell specification factors, and cell adhesion.