A small-molecule inhibitor of the serine-threonine kinase Aurora B with potential antineoplastic activity. Aurora B kinase inhibitor TAK-901 binds to and inhibits the activity of Aurora B, which may result in a decrease in the proliferation of tumor cells that overexpress Aurora B. Aurora B is a positive regulator of mitosis that functions in the attachment of the mitotic spindle to the centromere; the segregation of sister chromatids to each daughter cell; and the separation of daughter cells during cytokinesis. This serine/threonine kinase may be amplified and overexpressed by a variety of cancer cell types.