MCL1 and chronic myelogenous leukemia, BCR-ABL1 positive: To clearly prove that the potential off-target effects of imatinib [25, 26] do not play a key role in the synergistic interaction of MCL1 inhibition and imatinib treatment, we analyzed the effects of the two drugs and their combinations on the imatinib-sensitive parental TCCS and K562 CML lines (harboring wild-type BCR-ABL1) and their imatinib resistant sublines harboring the T315I mutation in BCR-ABL1 (TCCST315I and K562T315I), generated by HR using the CRISPR/Cas9 system [19].