The following article features coverage from the American Society of Clinical Oncology 2019 meeting. Click here to read more of Hematology Advisor’s conference coverage.

Bosutinib may be a safe and efficacious treatment option for patients with Philadelphia-positive (Ph+) chronic-phase (CP) chronic myeloid leukemia (CML), according to results from the phase 4 BYOND study (ClinicalTrials.gov Identifier: NCT02228382) presented at the 2019 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, Illinois.

In total, 163 patients received bosutinib, 156 of whom had Ph+ CP CML and had been pretreated with 1, 2, or 3 other tyrosine kinase inhibitors (TKIs). Bosutinib dosage started at 500 mg/day and was adjusted as needed due to adverse events. Cumulative confirmed major cytogenetic response was the primary endpoint. Cumulative rates of molecular response and adverse events were also assessed.

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After a median follow-up of 20.4 months, 56.4% of patients remained on bosutinib. Adverse events led to discontinuation in 25.0% of patients, while 5.1% of patients discontinued treatment due to insufficient response. Median duration of treatment was 23.7 months, and median dosage was 313 mg/day.

Overall survival at 1 year was 98.0%. Of 144 evaluable patients who had valid baseline assessments, 71.5% achieved confirmed major cytogenetic response within 1 year of starting treatment, and 81.3% of experienced complete cytogenetic response at some point during treatment.

Major molecular response was achieved by 56.3% of patients with 3 prior TKIs, 76.4% of patients with 2 prior TKIs, and 82.6% of patients with 1 prior TKI. Deep molecular response was achieved by 39.6% of patients with 3 prior TKIs, 61.8% of patients with 2 prior TKIs, and 69.6% of patients with 1 prior TKI.

Diarrhea and nausea were the most common treatment-emergent adverse events, occurring in 87.8% and 41.0% of patients, respectively. Diarrhea and increased alanine aminotransferase (ALT) were the only grade 3 or 4 adverse events with incidence greater than 10%, and increased ALT was the only adverse event that resulted in treatment discontinuation in more than 5% of patients.

“[These] results further support bosutinib use for Ph+ CP CML resistant or intolerant to prior TKIs,” the researchers wrote.

Reference

1.     Gambacorti-Passerini C, Abboud CN, Gjertsen BT, et al. Primary results of the phase 4 BYOND study of bosutinib (BOS) for pretreated chronic phase (CP) chronic myeloid leukemia (CML). Poster presentation at: 2019 ASCO Annual Meeting; June 3, 2019; Chicago, IL. Abstract 7012.