PHA-680626 is a potent and selective PLK inhibitor. PHA-680626 exhibits anti-proliferative and pro-apoptotic activity on Imatinib-resistant chronic myeloid leukemia cell lines and primary CD34+ cells by inhibition of both Bcr-Abl tyrosine kinase and Aurora kinases. PHA-680626 inhibits Plk1 (IC50 = 0.53 μM), Plk2 (IC50 = 0.07 μM) and Plk3 (IC50 = 1.61 μM).