An inhibitor of MPS1/TTK (IC50 = 5.8 nM); inhibits MPS1 phosphorylation of KNL1 and increases the rate of mitosis at 100 nM; increases the number of missegregated chromosomes at 50 and 100 nM; inhibits colony formation of DLD1, HCT116, and U2OS cells (IC50s = 24.6, 20.1, and 20.6 nM, respectively)