From 253 CML patients diagnosed within the years 2010-2018 and treated with TKIs as frontline therapy 87 responded to therapy as warning or failure according to the ELN recommendation.1 This group of non-optimally responded patients were regularly evaluated for the presence of BCR-ABL1 KD mutations. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.