(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.