In this study, we demonstrate that the gene expression levels of ESPL1/Separase and two functionally associated genes, PTTG1/Securin and PTTG1IP (Securin interacting protein), can have a predictive value for achievement of MMR under TKI first-line therapy within 12 months for a distinct set of newly diagnosed CML patients. Here, PTTG1 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.