Treatment of chronic myeloid leukemia (CML) has advanced with the introduction of tyrosine kinase inhibitors (TKI) that target the BCR-ABL1 fusion protein such as imatinib, and furthermore with second line inhibitors such as dasatinib, nilotinib, bosutinib and ponatinib. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.