A-1331852 displayed remarkable potency, both as a single agent and in combination with TKIs, to induce apoptosis in cell lines and in progenitor CD34+ primary cells (Figures 5 and 6) demonstrating the critical importance of BCL-XL in the survival of CML cells. This evidence concerns the gene BCL2L1 and chronic myelogenous leukemia, BCR-ABL1 positive.