A potent inhibitor of MPS1 (IC50 = 1.8 nM); selective for MPS1 over a panel of 79 kinases at a concentration of 500 nM; induces time-dependent degradation of cyclin B and securin and decreases phosphorylation of BUBR1 resulting in failed cytokinesis in HeLa cells arrested by nocodazole; causes misalignment of chromosomes at the anaphase plate and aneuploidy in A549 cells and slows cell cycle progression of HCT116 and COLO 205 cells irrespective of p53 activity; reduces tumor volume in an HCT116 mouse colon cancer xenograft model in a dose-dependent manner,