A potent Aurora kinase inhibitor (Kis = 8.0 and 9.2 nM for Aurora A and B kinases, respectively); selective over against a panel of CDKs and other kinases, with the exception of Flt-3 (Ki = 44 nM); exhibits broad-spectrum antiproliferative activity against a panel of human cancer cell lines (mean IC50 = 0.54 μM); orally bioavailable