Cyclin-dependent kinase inhibitor. IC50 values are 4, 70, 35, 850 and 75 nM for cdc2/cyclin B, cdk2/cyclin A, cdk2/cyclin E, cdk4/cyclin D1 and cdk5-p35 respectively. Reversibly arrests synchronised cells in G1 and G2, and inhibits cell proliferation and cell death.