Most pretreated patients with Philadelphia chromosome–positive (Ph+ CP) chronic myeloid leukemia (CML) experienced confirmed major cytogenetic response (cMCyR) within one year of treatment with the tyrosine kinase inhibitor (TKI) bosutinib, according to the findings of a study published in the SOHO 2019 Meeting Proceedings Supplement in Clinical Lymphoma, Myeloma and Leukemia.
The study design was phase 4 of the BYOND study in which researchers assessed the efficacy and safety of taking daily bosutinib (starting dose 500 mg/day) in 163 patients (52% male, median age, 61) TKI-resistant/intolerant CML. The primary outcome in Ph+ CP CML patients was specified as cumulative confirmed cMCyR by the end of one year.
According to the results of the study, after one-year cumulative cMCyR was 71.5% (95% confidence interval [CI] 63.4 to 78.7). The researchers observed 81.3% (95% CI, 83.9 to 87.3) cumulative complete cytogenetic response rate anytime on treatment: 81.3% (95% CI, 73.9 to 87.3). Cumulative major molecular response (MMR) rates were 71.8% (95% CI, 63.9 to 78.9), 82.6% (95% CI, 68.6 to 92.2), 76.4% (95% CI, 63.0 to 86.8), and 56.3% (95% 41.2 to 70.5) in total, 1, 2 and 3 prior TKIs patients, respectively.
“Most pretreated patients with Ph+ CP CML had MCyR by 1 year with bosutinib, and a substantial proportion achieved or preserved major and deep MR in all therapy lines,” the authors wrote in conclusion. “Results further support the use of bosutinib for TKI-resistant/intolerant Ph+ CP CML.”
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