ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: However, further clinical investigations demonstrated that once-daily dosing of dasatinib was as efficient and less toxic as twice-daily dosing.7,8 Thereafter, in vitro studies showed that a transient inhibition of BCR-ABL1 activity was sufficient to commit CML cells irreversibly to apoptosis9,10 even though CRKL phosphorylation was recovered.