To study the efficacy and safety of combination of Ro-Peg-interferon-α2b (RoPegIFN) with Bosutinib (BOS) in comparison to BOS monotherapy, as frontline therapy for newly diagnosed chronic myeloid leukemia patients, and to estimate efficacy of the addition of RoPegIFN to BOS in terms of deep molecular response with the aim of increasing the proportion of patients who may achieve treatment free remission. (NCMLSG study #NordCML012)

Inclusion Criteria:

• Signed written informed consent form (ICF) before any procedure related to the study
• Newly diagnosed (≤ 3 months) BCR-ABL positive chronic myeloid leukemia (CML) in chronic phase
• Major BCR-ABL transcripts (p210 b2a2(e13a2) and/or b3a2 (e14a2)
• Not previously treated for CML except with hydroxyurea or anagrelide
• ECOG Performance Status (ECOG PS) ≤ 2
• Adequate organ function: Total bilirubin < 1,5 times the institutional Upper Limit of Normal (ULN); Hepatic enzymes ASAT and ALAT < 2 times the institutional ULN; Serum Creatinine < 1.5 time the institutional ULN; Lipase < 1.5 time the institutional ULN
• Women of childbearing potential (WOCBP) must be using an adequate method of contraception to avoid pregnancy throughout the study.
• WOCBP must have a negative serum or urine pregnancy test at screening.
• Free subject, without guardianship nor subordination
• Health insurance coverage

Exclusion Criteria:

• Patients with BCR-ABL transcript other than M-BCR-ABL
• Patients previously treated with tyrosine kinase inhibitors (TKIs).
• Inability to freely provide consent through judiciary or administrative condition.
• Ongoing participation to another clinical investigational study.
• Medical history and concurrent diseases: a) Hypersensitivity to any of the excipients of BOS or RoPegIFN, b) Prior treatment with Interferon-α, contraindication to interferon-α, c) Autoimmune disorder, concomitant immunosuppressive treatment or corticosteroids, d) Pre-existing thyroid disease unless controlled with conventional treatment, auto-immune thyroiditis, e) Chronic liver disease, f) Prior or ongoing severe psychiatric disease, g) HIV positivity, chronic hepatitis B or C, h) Uncontrolled or severe cardiac (NYHA Class III or IV) or pulmonary disease, echocardiography with LVF < 45% or LLN, peak velocity of tricuspid regurgitant flow > 2,8 m/s, pulmonary arterial hypertension (PAH), QTc>450 ms (by Barrets correction)
• Other malignant disease during the last 5 years prior to the inclusion except non-melanoma skin carcinoma or carcinoma in situ of the cervix,
• History of significant bleeding disorder unrelated to CML or diagnosed congenital bleeding disorder,
• Subjects with an uncontrolled undercurrent illness or any concurrent condition that, in the investigator's opinion, would jeopardize the safety of the subject or compliance with the protocol.
• Prohibited treatments and/or therapies: strong inhibitors/inducers of the CYP 3A4,
• History / any condition for poor compliance to medical treatment.
• Women who are pregnant or breastfeeding are not eligible for this study