Cyclin-dependent kinase inhibitor that competes for the ATP binding site of the kinase. Selectively inhibits cdc2/cyclin B (IC50 = 7 μM), cdk2/cyclin A (IC50 = 7 μM), cdk2/cyclin E (IC50 = 7 μM), cdk/p35 kinase (IC50 = 3 μM) and ERK1/MAP kinase (IC50 = 25 μM). Arrests human fibroblasts in the G1 phase.