TDZD-8 is a thiadiazolidine derivative that acts as a non-ATP competitive inhibitor of the serine/threonine kinase glycogen synthase kinase 3β (GSK3β; IC50 = 2 μM), binding to the active site of GSK3β. It does not significantly affect the activities of Cdk-1/cyclin B, CK-II, cAMP-dependent protein kinase, or protein kinase C (IC50s = >100 μM). TDZD-8 has been used to study the role of GSK3β during stem cell differentiation as well as in cell and animal models of Alzheimer’s disease and other neurodegenerative disorders.