Glycogen Synthase Kinase-3? is a highly conserved ubiquitously expressed serine/threonine protein kinase involved in signal transduction cascades of multiple cellular processes. TDZD-8 is a thiadiazolidinone (TDZD) analogue that acts as a highly selective, non-ATP competitive inhibitor of GSK-3? ( IC50 =2nM). Binds to the active site of GSK-3?. Does not significantly affect the activities of Cdk-1/cyclin B, CK-II, PKA, and PKC (IC50 >100nM).