A dihydropteridinone that inhibits Plk1, Plk2, and Plk3 (IC₅₀s = 0.87, 5, and 56 nM, respectively), inducing mitotic arrest and apoptosis; inhibits proliferation of multiple cancer cell lines (EC₅₀s = 11-37 nM) and prevents the growth of various human carcinoma xenografts in mice.