Comparison of Frequency and Sensitivity of BCR-ABL1 Kinase Domain Mutations in Asian and White Patients With Imatinib-resistant Chronic-Phase Chronic Myeloid Leukemia.

INTRODUCTION: BCR-ABL1 mutations require consideration during second-line tyrosine kinase inhibitor selection for patients with chronic myeloid leukemia (CML). The present retrospective analysis compared the frequency of BCR-ABL1 mutations in Asian and white patients in whom imatinib therapy had failed. PATIENTS AND METHODS: A nonstudy cohort (76 Asian patients from community clinical practices) and 2 study cohorts (29 Asian and 352 white patients from dasatinib phase II and III clinical trials) were identified. RESULTS: In the nonstudy cohort, 80 mutations were identified; the most frequent was T315I (15%), followed by phosphate-binding loop mutations E255K (11%), G250E (10%), and Y253H (10%). Asian patients had a greater proportion of T315I and phosphate-binding loop mutations compared with the white patients. The nonstudy cohort was less likely to have multiple mutations compared with either study cohort. Single mutations highly resistant to dasatinib, nilotinib, and bosutinib were more frequent in the Asian than in the white cohorts. CONCLUSION: These results suggest that mutational analysis findings will be invaluable for choosing an appropriate second-line tyrosine kinase inhibitor in Asia.

Nilotinib as frontline therapy for patients with newly diagnosed Ph+ chronic myeloid leukemia in chronic phase: results from the Japanese subgroup of ENESTnd.

Recent results from the phase 3 ENESTnd (Evaluating Nilotinib Efficacy and Safety in Clinical Trials-Newly Diagnosed Patients) study have demonstrated superiority of nilotinib over imatinib for the treatment of newly diagnosed Philadelphia chromosome-positive chronic myeloid leukemia in the chronic phase (CML-CP). Here, we report results from the Japanese subset of patients in ENESTnd, and assess whether results in this subpopulation are consistent with the overall study population. Seventy-nine Japanese patients with CML-CP were randomized to receive nilotinib 300 mg twice daily (BID) (n = 30), nilotinib 400 mg BID (n = 24) or imatinib 400 mg once daily (QD) (n = 25). Major molecular response rates at 12 months, the primary endpoint, were at least twice as high for nilotinib 300 mg BID (57%) and nilotinib 400 mg BID (50%) compared with imatinib 400 mg QD (24%). No patient on nilotinib progressed, while one patient progressed on imatinib. Both drugs were generally well tolerated and discontinuations due to adverse events were comparable among treatment arms. The results in the subpopulation of Japanese patients from ENESTnd closely mirror the results of the overall population, and support the use of nilotinib at 300 mg BID in Japanese patients with newly diagnosed CML-CP.