Inclusion Criteria:

• Patients ≥18 years old
• Diagnosis of chronic myeloid leukemia associated with BCR-ABL quantifiable by RQ-PCR
• Documented CCyR by bone marrow or BCR-ABL<1% IS in the past 12 months
• Persistent disease demonstrated by two PCR positive tests 3 months apart both during the past 6 months.
• Treatment with imatinib for at least 2 years with 400 mg or 600 mg and a stable dose
• No other current or planned anti-leukemia therapies

Exclusion Criteria:

• Patient has evidence of rising PCR (a confirmed >1 log increase in previous 6 months)
• Patient has received another investigational agent within last 6 months or TKIs other than imatinib
• Prior allogeneic stem cell transplantation

• Impaired cardiac function including any one of the following:

  • LVEF < 45% or below the institutional lower limit of the normal range (whichever is higher) as determined by echocardiogram in the presence of symptoms of heart failure
  • Inability to monitor the QT interval on ECG
  • Long QT syndrome or a known family history of long QT syndrome.
  • Clinically significant resting brachycardia (<50 beats per minute)
  • QTc > 450 msec on baseline ECG (using the QTcF formula). If QTcF >450 msec and electrolytes are not within normal ranges, electrolytes should be corrected and then the patient re-screened for QTc
  • Myocardial infarction within 12 months prior to starting study
  • Other clinically significant uncontrolled heart disease (e.g. unstable angina, congestive heart failure or uncontrolled hypertension)
  • History of or presence of clinically significant ventricular or atrial tachyarrhythmias
• Administration of cytokine therapy (e.g. G-CSF, GM-CSF or SCF) within 4 weeks prior to study entry