Efficacy and safety of bosutinib for previously treated chronic myeloid leukemia: final results from the phase 4 BYOND trial

Bosutinib is an orally bioavailable, multi-targeted Src-Abl tyrosine kinase inhibitor that has been approved for patients with previously treated Ph+ chronic myeloid leukemia (CML) based on the results from a phase 1-2 trial that demonstrated durable efficacy and a tolerable safety profile. The phase 4 BYOND trial further evaluated the efficacy and safety of bosutinib for previously treated CML. Final results of BYOND have now been published. At study completion (median follow-up 47.8 months), 48.1% of Ph+ CML were still receiving treatment. Among evaluable patients, 71.8% (95% CI 63.9-78.9) and 59.7% (51.4-67.7) attained or maintained major moleculare response (MMR) and molecular response (MR)⁴, respectively, at any time on treatment. Kaplan-Meier probabilities of maintaining MMR and MR⁴ at 36 months were 87.2% (95% CI 78.0-92.7) and 80.7% (69.4-88.1), respectively. At 48 months, the overall survival rate was 88.3% (95% CI 81.8-92.6); there were 17 deaths, including 2 that were considered CML related. There were no new safety signals. The authors conclude that these results support the use of bosutinib in patients with previously treated CML.