BCR and chronic myelogenous leukemia, BCR-ABL1 positive: However, we observed a phosphorylation reduction in STAT5, indicating that, in contrast to CML, the antileukemic effect of Venetoclax, could be dependent on its ability to interfere with pro-survival intracellular signaling mediated by BCR-ABL1 and STAT5 in Ph+ B-ALL cells.