Nilotinib Versus Standard Imatinib (400/600 mg Every Day (QD)) Comparing the Kinetics of Complete Molecular Response for Chronic Myelogenous Leukemia in Chronic Phase (CML-CP) Pts With Evidence of Persistent Leukemia by Real-time Quantitative Polymerase Chain Reaction (RQ-PCR)

Inclusion Criteria:

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 tyrosine kinase inhibitors (TKIs) other than imatinib Prior allogeneic stem cell transplantation

Impaired cardiac function including any one of the following:

Inability to monitor the QT interval on electrocardiogram (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