ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Imatinib is a tyrosine kinase inhibitor (TKI) that was approved by the FDA in 2001 for the treatment of Philadelphia chromosome-positive (Ph+) chronic myelogenous leukemia (CML) where a characteristic cytogenetic translocation t (9;22) leads to the rearrangement of the breakpoint cluster region (BCR) and Abelson (ABL) genes.