BCR and chronic myelogenous leukemia, BCR-ABL1 positive: To clarify, whether the wash-out regimen used affected drug efficacy, we set up experiments with serial drug wash-out procedures to observe the effects on cell death: Ba/F3 BCR-ABL cells and K562 cells (a CML blast crisis cell-line) were either treated with 25 μM imatinib or 100 nM dasatinib for 2 h followed by three consecutive rounds of thorough medium exchange (each consisted of 2 washing steps) at 2 h intervals.