Indeed, about 15%–30% of newly diagnosed chronic phase (CP)-CML patients will not reach an optimal response with first-line tyrosine kinase inhibitors (TKIs) therapy, and in about 25%–50% of them a BCR-ABL1 KD mutation will be identified (Soverini et al., 2011). The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.