MCL1 and chronic myelogenous leukemia, BCR-ABL1 positive: More importantly, we showed that combination treatment with antitumorigenic concentrations of S63845 and imatinib does not significantly potentiate the anticlonogenic effect of imatinib on normal human hematopoietic stem/progenitor cells, suggesting that a suitable therapeutic window for combination treatment with a small-molecule MCL1 inhibitor and a TKI might be achievable in CML patients.