Efficacy and Safety of Bosutinib in Previously Treated Patients with Chronic Myeloid Leukemia: Final Results from the Byond Trial
Authors: Gambacorti-Passerini Carlo , Brümmendorf Tim H , Abruzzese Elisabetta , Kelly Kevin R. , Oehler Vivian G. , Garcia-Gutiérrez Valentín , Hjorth-Hansen Henrik , Ernst Thomas , Leip Eric , Purcell Simon , Luscan Gerald , Viqueira Andrea , Giles Frank , Hochhaus Andreas 
Published: November 2021

Abstract
Introduction: Bosutinib is approved for patients with Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) resistant/intolerant to prior therapy and patients with newly diagnosed Ph+ chronic phase (CP) CML. The phase 4 BYOND trial (NCT02228382) further evaluated the efficacy and safety of bosutinib in patients with previously treated CML. We report the final results from BYOND.
Methods: Patients with CML resistant/intolerant to previous tyrosine kinase inhibitor therapy received bosutinib 500 mg once daily. This final analysis was based on a November 23, 2020 database lock, after 3 years of follow-up.
Results: Of 163 patients who received bosutinib, 156 had Ph+ CP CML; 4 patients with accelerated phase CML and 3 with Ph−/BCR-ABL1+ CML were analyzed separately. At study completion (median follow-up, 47.8 months), 48.1% of patient with Ph+ CP CML were still receiving treatment, and 68.6% completed the study. Most common primary reason for treatment discontinuation was adverse events (AEs) (26.9% [n=42/156]). Median treatment duration was 40.9 months (range, 0.2−50.1) and median dose intensity 306.4 mg/day (range, 79.7−560.6). Dose interruptions due to AEs occurred in 76.3% of patients and dose reductions in 79.5% of patients. Dose reduction (without further reduction) to 400, 300, or 200 mg/day occurred in 35 (22.4%), 46 (29.5%), and 38 (24.4%) patients, respectively.
In evaluable patients with Ph+ CP CML, 81.1% (95% CI: 73.7-87.2), 71.8% (95% CI: 63.9-78.9), 59.7% (95% CI: 51.4-67.7) and 48.3% (95% CI: 40.1−56.6) attained or maintained complete cytogenetic response, major molecular response (MMR), MR 4, and MR 4.5 respectively, at any time on treatment. The majority of patients achieved a deeper molecular response relative to baseline while on bosutinib (Table 1). Among responders, the Kaplan-Meier probabilities (95% CI) of maintaining MMR and MR 4 at 36 months were 87.2% (78.0−92.7) and 80.7% (69.4−88.1), respectively. No patients with Ph+ CP CML progressed to accelerated/blast phase on-treatment. At 48 months, the cumulative incidence of progression free-survival events was 5.1% (95% CI: 2.4-9.4) and the Kaplan-Meier overall survival rate 88.3% (95% CI: 81.8-92.6). There were 17 deaths; 2 were considered CML-related (off-treatment progression to AP/BP, n=1; cardiogenic shock, n=1) and none were considered to be treatment-related by the investigator.
In the overall patient population (N=163), any grade treatment-emergent AEs (TEAEs) were reported by 99.4% of patients and grade 3/4 TEAEs were reported by 79.1% of patients (Table 2). Most common (≥10%) TEAEs leading to dose reduction were diarrhea (27.0%) and increased ALT (12.3%) and most common TEAEs leading to temporary dose interruption were diarrhea (30.7%), increased ALT (14.7%), vomiting (13.5%), increased AST (11.0%), and nausea (10.4%). AEs leading to treatment discontinuation in ≥2% of patients were increased ALT (4.9%) and AST (2.5%).
Conclusions: After 3 years, bosutinib continued to show efficacy in previously treated patients with Ph+ CP CML. Long-term AEs were generally manageable and consistent with previous reports of bosutinib. These results confirm the use of bosutinib as a standard of care in previously treated patients with CML.
Figure 1 Figure 1.

Disclosures
Gambacorti-Passerini: Pfizer: Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy. Brümmendorf: Bristol Myers: Research Funding; Novartis: Honoraria, Patents & Royalties, Research Funding; Janssen: Honoraria; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Repeat Diagnostics: Research Funding; Takepart Media: Honoraria. Abruzzese: Incyte: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria. Kelly: Takeda: Consultancy; AstraZeneca: Consultancy; Sanofi-Aventis: Consultancy; Denovo Biopharma: Consultancy; Verastem: Consultancy; Amgen: Consultancy; Berkley Lights: Current equity holder in publicly-traded company; Agios: Current equity holder in publicly-traded company; Bayer: Speakers Bureau; Janssen: Speakers Bureau; Novartis: Speakers Bureau; Celgene: Speakers Bureau; Epizyme: Speakers Bureau; Pharmacyclics: Speakers Bureau; Karyopharm: Speakers Bureau; Gilead: Speakers Bureau. Oehler: OncLive: Honoraria; Takeda: Consultancy; Pfizer: Research Funding; BMS: Consultancy. Garcia-Gutiérrez: Bristol-Myers Squibb: Consultancy; Novartis: Consultancy; Incyte: Consultancy; Pfizer: Research Funding. Hjorth-Hansen: Pfizer: Research Funding; Novartis: Research Funding; AOP: Research Funding. Leip: Pfizer: Current Employment, Current equity holder in publicly-traded company. Purcell: Pfizer: Current Employment, Current equity holder in publicly-traded company. Luscan: Pfizer: Current Employment, Current equity holder in publicly-traded company. Viqueira: Pfizer: Current Employment, Current equity holder in publicly-traded company. Giles: Novartis: Consultancy; Actutate Therapeutics: Current Employment; Epigene Therapeutics: Consultancy, Current equity holder in publicly-traded company. Hochhaus: Pfizer: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Research Funding; Incyte: Research Funding.