Molecular response must be assessed according to the International Scale (BCR::ABL1IS) using ABL1, BCR, or GUSB as internal reference genes for patients expressing standard e13a2 and/or e14a2 BCR::ABL1 mRNA variants (98% of CML patients) [7]. The gene discussed is GUSB; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.