An inhibitor of the cyclin-dependent kinases Cdk1/cyclin B, Cdk2/cyclin E, and Cdk4/cyclin D1 (Kis = 1-3 nM); inhibits tumor cell proliferation (IC50s ≤ 0.6 µM in vitro), inducing cell cycle arrest and apoptosis as well as reducing phosphorylation of the retinoblastoma protein.