This trial will use a combination of asciminib 40 mg by mouth (PO) twice daily (BID) plus imatinib (maximum dose of 400 mg PO once daily) in the combination treatment phase. The BCR-ABL tyrosine kinase inhibitor (TKI) that will be used for this trial is imatinib. All eligible patients will begin asciminib in combination with imatinib on cycle 1 day 1 of the combination phase. They will continue combination therapy for a total of 12 cycles (minimum of 12 months). Each cycle will be ~28 days. At the end of 12 cycles asciminib will be discontinued and any patient who has met the criteria for the treatment-free remission (TFR) screening phase will enter into the TFR phase. Once in the TFR phase, patients will discontinue their imatinib and be monitored off treatment. The primary endpoint of this study is the 12-month second TFR rate after completion of 12 cycles of combination therapy. Patients will remain in the TFR phase of the study for up to three years and will have central polymerase chain reaction (PCR) testing during the first two years. Therefore, the total duration of the subject participation trial will be approximately five years (one year on combination treatment phase plus three years in the TFR phase plus one year of long-term follow-up post TFR or early discontinuation.
This is a single-arm phase II study that will enroll a minimum of 41 subjects with a maximum of 51. All patients will have a confirmed diagnosis of chronic phase chronic myeloid Leukemia and must have previously attempted to discontinue imatinib. All patients must be restarted on imatinib at the time of relapse in order to be eligible for this trial.