A small-molecule inhibitor of Aurora kinases A, B and C with potential antineoplastic activity. Aurora kinase inhibitor AMG 900 selectively binds to and inhibits the activities of Aurora kinases A, B and C, which may result in inhibition of cellular division and proliferation in tumor cells that overexpress these kinases. Aurora kinases are serine-threonine kinases that play essential roles in mitotic checkpoint control during mitosis and are overexpressed by a wide variety of cancer cell types.