An orally available, Polo-like kinase 1 (PLK1) inhibitor with potential antineoplastic activity. Polo-like kinase 1 inhibitor TAK-960 selectively inhibits PLK1, inducing selective G2/M cell-cycle arrest followed by apoptosis in a variety of tumor cells while causing reversible cell-cycle arrest at the G1 and G2 stages without apoptosis in normal cells. PLK1 inhibition may result in the inhibition of proliferation in PLK1-overexpressed tumor cells. PLK1, named after the polo gene of Drosophila melanogaster, is a serine/threonine kinase crucial in the regulation of mitosis.