(1R,?2S)?-2-?[3-?[(1E)?-?2-?[4-?[[(2R,?6S)?-?2,?6-?Dimethyl-?4-?morpholinyl]?methyl]?phenyl]?ethenyl]?-?1H-?indazol-?6-?yl]?-?5'-?methoxy-?spiro[cyclopropane-?1,?3'-?[3H]?indol]?-?2'(1'H)?-?one selectively inhibits polo-like kinase 4 (PLK4), which is a serine/threonine protein kinase that regulates centriole duplication during the cell cycle. PLK4 is a therapeutic target for various cancers.