Inclusion Criteria:

- Adult patients >or = 18 years

- Diagnostic of Ph+ Chronic Myeloid Leukemia in first chronic phase

- Treated with Imatinib 400 mg per day or 600 mg per day for at least 18 months. A wash
out period of at least 7 days for imatinib is required prior to dasatinib
administration

- Patients meet criteria of late suboptimal response (complete cytogenetic response
with no major molecular response) or have lost major molecular response

- Ability to understand and voluntarily sign the informed consent for

- Women of childbearing potential (WOCBP) must be using an adequate method of
contraception to avoid pregnancy and have a negative pregnancy test, a maximum of 72
hours prior to study drug start.

Sexually active men must also use effective contraceptive methods during the treatment.

- Women must not be breastfeeding

Exclusion Criteria:

- Patients treated with Imatinib at a dose different of 400/600 mg per day

- Patients treated with other TKI than imatinib

- Loss of cytogenetic response at study entry

- ECOG ≥ 3

- Inadequate bone marrow reserve: ANC <1.5 x 109/L and/or Platelet count < 100 x 109/L

- Inadequate hepatic function (Alanine aminotransferase (ALT) and/or aspartate
aminotransferase (AST)> 2.5 X institutional upper limit of normal (IULN). Total
bilirubin > 1.5 X IULN (unless Gilbert syndrome has been diagnosed)

- Inadequate renal function (serum Cr >3 UNL or ClCr <45 ml/min)

- Patients receiving concurrent treatment with other experimental drugs or anti-cancer
therapy

- Patients with uncontrolled concurrent disease:

Known pleural effusion at baseline Clinically-significant gastrointestinal disease or
surgery that would compromise absorption of study drug (eg, uncontrolled nausea or
malabsorption syndrome) Clinically-significant known coagulation or platelet function
disorder (not related to thrombocytopenia), eg, von Willebrand's disease Other active
malignancy requiring concurrent intervention

Uncontrolled or significant cardiovascular disease, including any of the following:

Myocardial infarction within 6 months of enrolment date Uncontrolled angina or congestive
heart failure within 3 months of enrolment date Left ventricular ejection fraction (LVEF)
< 40% Significant cardiac conduction abnormality, including history of
clinically-significant ventricular arrhythmia (such as ventricular tachycardia,
ventricular fibrillation, or Torsades de Pointes), history of third degree heart block or
diagnosed congenital long QT syndrome, and/or prolonged QTc/f interval > 450 msec on
baseline ECG.

- Patients with active or uncontrolled infections or with serious illnesses or medical
conditions that would not permit the patient to be managed according to the protocol.

- Patients unable or unwilling to give written, informed consent prior to study
participation.