Deep molecular responses (DMRs), i.e. ≥ 4-log (MR4) reduction of BCR-ABL1 transcript levels below the standardized baseline on the International Scale (BCR-ABL1IS), are discussed as a new goal of CML therapy [9, 15, 16]. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.