Patients with chronic myeloid leukemia in chronic phase (CML-CP) resistant or intolerant to ≥2 tyrosine kinase inhibitors (TKIs) are at high risk of experiencing poor outcomes due to disease biology and inadequate efficacy and/or safety of current therapies. Asciminib is a first-in-class STAMP (Specifically Targeting the ABL Myristoyl Pocket) inhibitor with the potential to overcome resistance or intolerance to approved TKIs. In this phase 3, open-label study, patients with CML-CP previously treated with ≥2 TKIs were randomized (2:1) to receive asciminib 40 mg twice daily vs bosutinib 500 mg once daily. Randomization was stratified by major cytogenetic response (MCyR) status at baseline. The primary objective was to compare the major molecular response (MMR) rate at week 24 for asciminib vs bosutinib. Two hundred and thirty-three patients were randomized to asciminib (n=157) or bosutinib (n=76). Median follow-up was 14.9 months. The MMR rate at week 24 was 25.5% with asciminib and 13.2% with bosutinib. The difference in MMR rate between treatment arms, after adjusting for MCyR at baseline, was 12.2% (95% CI, 2.19-22.30; 2-sided P=.029). Fewer grade ≥3 adverse events (50.6% vs 60.5%) and fewer adverse events leading to treatment discontinuation (5.8% vs 21.1%) occurred with asciminib than with bosutinib. The study showed a superior efficacy of asciminib compared with that of bosutinib, together with a favorable safety profile. These results support the use of asciminib as a new therapy in patients with CML-CP who are resistant or intolerant to ≥2 prior TKIs. The trial is registered at as NCT03106779.
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