[Key points in second-line therapy for chronic myeloid leukemia]

Tyrosine kinase inhibitors (TKIs) have markedly improved the prognosis of chronic myeloid leukemia (CML). In Japan, in addition to the four established first-line TKIs, asciminib is now approved as an initial therapy, expanding the treatment options. Nevertheless, more than 10% of patients treated with asciminib over 48 weeks, and approximately 20-30% of those receiving other TKIs over five years, require second-line therapy because of resistance or intolerance. As first-line choices diversify, selecting the optimal second-line regimen has become increasingly complex. For intolerance, switching should be guided by the adverse-event profile with attention to potential cross-intolerance. For resistance, assessment of BCR::ABL1 mutations is essential, and second-line agents should be chosen according to the initial TKI and mutation sensitivity. This article summarizes the criteria and timing for switching to second-line therapy and key considerations for selecting and managing second-line TKIs, and briefly reviews the evidence for asciminib and ponatinib in second-line and later settings.