We investigated differences in hOCT1 mRNA expression in different cell populations of PB leukocytes (LEU) from healthy volunteers and patients with de novo CML, a change in hOCT1 mRNA expression during the first 6 months of IMA treatment, and the relationship between hOCT1 mRNA expression and the percentage of immature myeloid cells as well as BCR/ ABL transcript levels in PB (as indirect markers of disease burden).