Valproic acid inhibits histone deacetylases (HDACs), in particular Class I HDACs. It is an analog of the natural fatty acid valeric acid. Valproic acid also inhibits GSK3 and depletes cellular inositol-1,4,5-triphosphate. It can have strong effects on stem cell differentiation and self-renewal, and it shows promise in treating cancer and Alzheimer’s disease.