STAT5A and chronic myelogenous leukemia, BCR-ABL1 positive: Nam and colleagues screened a number of indirubicin derivatives, demonstrating that the most potent compound (E804) blocked Stat5a/b phosphorylation at 10-20 μmol/L in K562 human chronic myelogenous leukemia (CML) cells positive for Bcr-Abl, which drives constitutive activation of Stat5a/b [215].