A cell-permeable indazolylimidazopyridazinamine compound that acts as a potent and reversible inhibitor of histone kinase haspin activity (IC50 = 2 nM) with moderate selectivity over TrkA, GSK-3β, PIM1, Cdk1/B and Cdk2/A (% inhibition at 100 nM = 58, 48, 36, 34 and 33, respectively) among a panel of 27-kinases. Shown to block pH3-Thr3, with no effect on pH3-Ser10 and pH3-Ser28, cause mitotic catastrophe, upregulate BUB1 and cyclin B1 levels, and potently induce apoptosis (IC50 = 473, 500 and 752 nM in HeLa, HCT-116 and MDA-MB-231 cells, respectively). Further, efficiently blocks bFGF-induced sprouting vessel by 70% at 1 μM (chicken embryo aortic arch ring assay) and suppresses tumor growth in HCT-116 xenografted mouse model (50 mg/kg, i.p.).
