Novel, selective ATP-competitive inhibitor of Aurora B kinase in vitro (IC50 values are 50, 250 and 1000 nM for Aurora B, C and A kinases respectively). Selective over a range of other kinases including cdk1 and PLK1 (IC50 > 10 μM). Inhibits cell division and displays selective toxicity towards proliferating tumor cells versus non-dividing cells.