• Patients who are 18 years or older

• Patients have a diagnosis of Philadelphia chromosome- or BCR-ABL1-positive CML (as determined by cytogenetics, FISH, or PCR).

• Prior evidence of a quantifiable BCR-ABL1 transcript by RT-PCR

• Patients who have been taking TKI for \> 36 months.

• Patients must have a history of stable molecular response, defined as MR4.5 for ≥24 months, as documented by ≥3 separate tests performed at least three months apart.

• Patient must have a current status of complete molecular remission (CMR), defined as MR4.5 (per section 5.1), within 30 days of signing consent.

• ECOG performance status \< 2

• Patients must have normal marrow function within 30 days of registration, as defined:

‣ Absolute Neutrophil Count (ANC) ≥ 1.5 x 10E9/L

⁃ Hemoglobin ≥ 9.0 g/dL

⁃ Platelets ≥ 100 x 10E9/L

• Patients must not have any signs of extramedullary leukemia

⁃ Patients must have a life expectancy of more than 12 months in the absence of any intervention

⁃ All participants must be informed of the investigational nature of this study and must sign and give written informed consent

⁃ Contraception requirements will be as per routine clinical practice.