ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: The first-generation ABL inhibitor, imatinib, has been used for decades to treat BCR-ABL1-driven chronic myelogenous leukemia (CML), and second (e.g. nilotinib) and third (e.g. ponatinib)-generation drugs were developed to combat imatinib resistance9.