A small-molecule 3-aminopyrazole derivative with potential antineoplastic activity. Aurora kinase inhibitor PHA-739358 binds to and inhibits the Aurora kinases, which may result in cell growth arrest and apoptosis in tumor cells in which Aurora kinases are overexpressed. This agent may preferentially bind to and inhibit Aurora B kinase. Aurora kinases, a family of serine-threonine kinases, are important regulators of cellular proliferation and division.