Cdk1 Inhibitor is an indolylmethylene-2-indolinone derivative that exhibits potent anti-proliferative properties (IC50 = 2 M HeLa cells). Cdk1 Inhibitor acts as a selective and ATP-competitive inhibitor of Cdk1/cyclin B (IC50 = 5.8 M). Also inhibits Cdk5 with a IC50 = 25 M. Binds to the ATP pocket on the Cdk1 active site. Does not affect the activity of GSK-3b even at 100 M concentrations.