Switching to nilotinib is associated with deeper molecular responses in chronic myeloid leukemia chronic phase with major molecular responses to imatinib: STAT1 trial in Japan

The purpose of this clinical trial was to evaluate the efficacy of 2-year consolidation therapy using nilotinib (NIL) for achieving a molecular response (MR^4.5, BCR-ABL1^IS ≤ 0.0032% on the International Scale) in patients with chronic myeloid leukemia in the chronic phase (CML-CP) who had achieved a major molecular response (MMR, BCR-ABL1^IS ≤ 0.1%) with imatinib (IM). We recruited 76 Japanese patients for this trial. Nilotinib 300 mg, twice daily, was administered for 2 years, and 74 patients were evaluated in the study. The median age was 55.0 years. The median duration of IM treatment was 69.0 months. All patients showed MMR at the time of entry into the study; the median time to MMR on IM therapy was 20.4 months. The proportion of patients who achieved MR^4.5 increased over time. The rates of MR^4.5 in the 74 evaluable patients were 27.0% [90% confidence interval (CI) (18.7–36.8%)] and 44.6% [90% CI (34.7–54.8%)] at 12 and 24 months, respectively. The frequency of ABCG2 421C/A + A/A was an independent predictive biomarker for achieving a 24-month MR^4.5. Switching to NIL led to safer, deeper molecular responses in patients with MMR on long-term IM therapy for future treatment-free remission.