Abstract: Bosutinib is approved for newly diagnosed Philadelphia chromosome-positive (Ph+) chronic phase (CP) chronic myeloid leukemia (CML) and for Ph+ CP, accelerated (AP), or blast (BP) phase CML after prior treatment with tyrosine kinase inhibitors (TKIs). In the ongoing phase 4 BYOND study (NCT02228382), 163 CML patients resistant/intolerant to prior TKIs ( n  = 156 Ph+ CP CML, n  = 4 Ph+ AP CML, n  = 3 Ph-negative/ BCR-ABL1 + CML) received bosutinib 500 mg once daily (starting dose). As of ≥1 year after last enrolled patient (median treatment duration 23.7 months), 56.4% of Ph+ CP CML patients remained on bosutinib. Primary endpoint of cumulative confirmed major cytogenetic response (MCyR) rate by 1 year was 75.8% in Ph+ CP CML patients after one or two prior TKIs and 62.2% after three prior TKIs. Cumulative complete cytogenetic response (CCyR) and major molecular response (MMR) rates by 1 year were 80.6% and 70.5%, respectively, in Ph+ CP CML patients overall. No patient progressed to AP/BP on treatment. Across all patients, the most common treatment-emergent adverse events were diarrhea (87.7%), nausea (39.9%), and vomiting (32.5%). The majority of patients had confirmed MCyR by 1 year and MMR by 1 year, further supporting bosutinib use for Ph+ CP CML patients resistant/intolerant to prior TKIs.

Abstract: 7012 Background: The tyrosine kinase inhibitor (TKI) BOS is approved for patients (pts) with Philadelphia chromosome (Ph)+ CML resistant/intolerant to prior therapy and newly diagnosed pts in CP. Methods: The ongoing phase 4 BYOND study is further evaluating efficacy and safety of BOS (starting dose 500 mg/d) for CML resistant/intolerant to prior TKIs. Primary endpoint (not powered) in Ph+ CP CML cohorts is cumulative confirmed major cytogenetic response (MCyR) by 1 y. Results: Of 163 pts who received BOS, 156 had Ph+ CP CML (46, 61 and 49 after 1, 2 and 3 prior TKIs, respectively). Across Ph+ CP CML cohorts, 51.9% of pts were male; median age was 61 y. As of 1 y after last enrolled pt (median follow-up 30.4 mo), 56.4% remained on BOS. Median BOS duration was 23.7 mo and median dose intensity after adjustment due to adverse events (AEs) 313 mg/d. Of 144 evaluable pts with a valid baseline assessment, cumulative confirmed MCyR by 1 y was 71.5% (95% confidence interval [CI] 63.4–78.7). Cumulative complete cytogenetic response rate anytime on treatment was 81.3% (95% CI 73.9–87.3). Cumulative molecular response (MR) rates were high across lines of therapy (Table). 10 deaths occurred (5 on treatment); 1-y overall survival rate was 98.0%. No pt progressed to accelerated/blast phase on treatment. 25.0% discontinued BOS due to AEs and 5.1% due to insufficient response. Most common treatment-emergent AEs (TEAEs) were diarrhea (87.8%) and nausea (41.0%). Grade 3/4 TEAEs in 〉 10% of pts were diarrhea (16.7%) and increased alanine aminotransferase (ALT; 14.7%). The only TEAE leading to discontinuation in 〉 5% of pts was increased ALT (5.1%). Conclusions: Most pretreated pts with Ph+ CP CML had MCyR by 1 y with BOS; a substantial proportion achieved or preserved major MR (MMR) and deep MR in all therapy lines. Results further support BOS use for Ph+ CP CML resistant/intolerant to prior TKIs. Clinical trial information: NCT02228382. [Table: see text]

Abstract: Background: Bosutinib is a tyrosine kinase inhibitor (TKI) approved for the treatment of Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) resistant/intolerant to prior therapy and newly diagnosed Ph+ chronic phase (CP) CML. The efficacy and safety of bosutinib by baseline comorbidities in patients with CML resistant/intolerant to prior TKIs were investigated. Methods: The phase 4 BYOND trial (NCT02228382) is further examining efficacy and safety of bosutinib (starting dose 500 mg/day) in patients with CML resistant/intolerant to prior TKIs. Comorbidities were analyzed using the Charlson Comorbidity Index (CCI), a validated measure of the influence of relevant comorbid conditions on mortality. Scores were derived from baseline data and patients grouped by CCI score 2-3, 4-5, and ≥6. This analysis was based on ≥1 year of follow-up and included patients with Ph+ CP CML. Results: 156 patients with Ph+ CP CML (n=42 [26.9%], 48 [30.8%] , and 66 [42.3%] for CCI 2-3, 4-5, and ≥6) received bosutinib. Median treatment duration was 28.9, 23.9, and 20.1 months for CCI 2-3, 4-5, and ≥6; median dose intensity was 366.7, 385.3, and 291.5 mg/day. Across CCI groups, a substantial proportion of patients attained/maintained cytogenetic and molecular responses (Table). Grade 3/4 treatment-emergent adverse events (TEAEs) rates were 64.3%, 72.9%, and 80.3% for CCI 2-3, 4-5, and ≥6. Emerging grade 3/4 TEAEs differed between groups; diarrhea and increased alanine aminotransferase (ALT) were more common for CCI 2-3 (21.4% and 23.8%, respectively) and 4-5 (18.8% and 16.7%) and pleural effusion more common for CCI ≥6 (12.1%). For CCI 2-3, 4-5, and ≥6, 19.0%, 20.8%, and 31.8% of patients discontinued treatment due to AEs and 2.4%, 2.1%, and 9.1% due to insufficient response. Most common AEs leading to discontinuation in the respective groups were increased ALT and aspartate aminotransferase (7.1% each), increased ALT (8.3%), and pleural effusion (3.0%). 10 deaths occurred (n=0 [0%] , 1 [2.1%], and 9 [13.6%] for CCI 2-3, 4-5, and ≥6), 8 due to AEs (none bosutinib-related), 1 CML-related, and 1 of unknown cause. No on-treatment transformations to advanced CML occurred. Conclusions: Across CCI groups, a majority of patients with Ph+ CP CML achieved/maintained cytogenetic and molecular responses, and only 1 CML-related death was reported. Patients with CCI ≥6 showed a trend toward higher rates of TEAEs, discontinuations due to AEs, and death. Results demonstrate efficacy of bosutinib across CCI scores, including patients with important comorbidities. However, CCI stratification may enable identification of patients at higher risk of developing TEAEs who require more careful monitoring. Disclosures Gambacorti-Passerini: Bristol-Meyers Squibb: Consultancy; Pfizer: Honoraria, Research Funding. Brümmendorf:Janssen: Consultancy; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Merck: Consultancy; University Hospital of the RWTH Aachen: Employment; Ariad: Consultancy. Gjertsen:Astellas: Consultancy; The Norwegian Cancer Society: Research Funding; BerGenBio: Consultancy; ERA PerMed: Research Funding; ACTII AS: Equity Ownership; Daiichi Sankyo: Consultancy; Seattle Genetics: Consultancy; Haukeland University Hospital / University of Bergen: Employment; KinN Therapeutics AS: Equity Ownership; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Helse Vest Health Trust: Research Funding; Research Council of Norway: Research Funding; EU Horizon 2020: Research Funding; BerGenBio AS: Membership on an entity's Board of Directors or advisory committees. Abboud:Jazz Pharma: Speakers Bureau; Novartis: Other: Member on an entity's Board of Directors or advisory committees (Ended 12/30/2017), Research Funding; Agios: Other: Member on an entity's Board of Directors or advisory committees (Ended 12/30/2017); Tetraphase Pharmaceuticals: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; NKarta: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Bayer: Consultancy, Honoraria. Rosti:BMS: Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Incyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Abruzzese:BMS: Consultancy; Incyte: Consultancy; Novartis: Consultancy; Pfizer: Consultancy. Leip:Pfizer: Employment, Equity Ownership. Viqueira:Pfizer Inc: Employment, Equity Ownership. García Gutiérrez:Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Incyte: Honoraria, Research Funding. Giles:Epigene Therapeutics Inc: Consultancy, Other: leadership, stock/other ownership ; Novartis: Consultancy; Actuate Therapeutics Inc: Employment. Hochhaus:Pfizer: Research Funding; Novartis: Research Funding; BMS: Research Funding; Incyte: Research Funding; MSD: Research Funding.

Abstract: Background: Bosutinib is approved at a starting dose of 500 mg once daily (QD) in patients with Philadelphia chromosome-positive chronic myeloid leukemia (CML) who are resistant or intolerant to prior treatment and at a starting dose of 400 mg QD in newly diagnosed patients with chronic phase (CP) CML. Approval of bosutinib after prior therapy was based on a phase 1/2 study in patients previously treated with imatinib ± dasatinib and/or nilotinib. After long-term follow-up (≥4 years), durable responses and maintenance of health-related quality of life (HRQoL) were seen in patients after prior imatinib (CP CML second-line [CP2L] cohort [n=284] ) or prior imatinib + dasatinib and/or nilotinib (CP CML third/fourth-line [CP3L/CP4L] cohort [n=115/4] ). As a post-authorization commitment to the European Medicines Agency, the BYOND study is providing additional safety and efficacy data for bosutinib in patients with CML after failure of prior tyrosine kinase inhibitor (TKI) treatment. Cumulative confirmed major cytogenetic response rate by 1 year (primary endpoint; not powered) in evaluable patients with CP CML was 75.8% after 1 or 2 prior TKIs (n=99) and 62.2% after 3 prior TKIs (n=45). Cumulative complete cytogenetic response rate anytime on treatment was 86.0%, 83.9%, and 73.3% in the CP2L, CP3L, and CP4L cohorts, respectively. Patients had high rates of molecular responses across all lines of treatment. Evaluation of HRQoL through patient-reported outcome (PRO) measures is an exploratory objective of BYOND. Methods: BYOND (NCT02228382) is an ongoing, phase 4, single-arm, open-label study of bosutinib at a starting dose of 500 mg QD in patients with CML and resistance/intolerance to prior treatment. At baseline and during treatment, patients were asked to complete the Functional Assessment of Cancer Therapy-Leukemia (FACT-Leu v4) instrument, a 44-item, valid assessment of HRQoL in patients with leukemia. Each item was scored on a scale from 0 to 4, with higher scores indicating better HRQoL. Changes in HRQoL that are clinically meaningful to a patient have been defined as the minimal important difference (MID) for most FACT-Leu domains. We report PRO results at Month 12 of bosutinib treatment in the CP CML cohorts; for comparison, we present PRO data at Month 12 from the CP CML cohorts of the phase 1/2 study of bosutinib in previously treated patients. Results: At baseline, most FACT-Leu scores were similar ( 〈 5% difference) in the CP2L and CP3L cohorts of the BYOND study (Table); social and functional well-being scores were lower and the emotional well-being score was higher in the CP2L cohort. Baseline FACT-Leu scores were lower in the CP4L cohort, with 〉 5% differences seen for physical and emotional well-being compared with the CP2L cohort, and for physical, social, and functional well-being, FACT-General (FACT-G) total, FACT-Leu total, and trial outcome index (TOI) FACT-Leu compared with the CP3L cohort. At Month 12, no mean change in a FACT-Leu domain score met the MID (Figure), indicating preservation of baseline HRQoL across all cohorts. Mean changes in FACT-Leu scores from baseline to Month 12 were similar in the CP2L cohorts of the BYOND study and the phase 1/2 study. HRQoL trends were also generally similar in the CP3L cohort of BYOND and the CP3L/4L cohort of the phase 1/2 study, in which 97% of patients received third-line bosutinib. Conclusions: HRQoL was maintained from baseline in patients with CP CML following 12 months of bosutinib treatment in the BYOND study. HRQoL changes at Month 12 were comparable to those observed in previously treated patients in the initial phase 1/2 study of bosutinib, wherein long-term efficacy and HRQoL stability were subsequently reported. In addition, FACT-G scores in the BYOND study were consistent with those previously reported for general populations as well as patients with various cancers. Maintenance of HRQoL is important for patients with CP CML who potentially will receive lifelong TKI treatment, and the PRO results from BYOND suggest bosutinib is a well-tolerated treatment option, thus providing further support for its use in patients with CP CML resistant/intolerant to prior TKIs. Relationships between molecular response and HRQoL in the BYOND study are being explored. Disclosures Brümmendorf: University Hospital of the RWTH Aachen: Employment; Merck: Consultancy; Ariad: Consultancy; Pfizer: Consultancy, Research Funding; Janssen: Consultancy; Novartis: Consultancy, Research Funding. Gambacorti-Passerini:Bristol-Meyers Squibb: Consultancy; Pfizer: Honoraria, Research Funding. Abboud:Jazz Pharma: Speakers Bureau; Novartis: Other: Member on an entity's Board of Directors or advisory committees (Ended 12/30/2017), Research Funding; Agios: Other: Member on an entity's Board of Directors or advisory committees (Ended 12/30/2017); Tetraphase Pharmaceuticals: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; NKarta: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Bayer: Consultancy, Honoraria. Watts:Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Rosti:BMS: Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Incyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Russell-Smith:Pfizer: Employment, Equity Ownership. Viqueira:Pfizer Inc: Employment, Equity Ownership. Reisman:Pfizer Inc: Employment, Equity Ownership. Giles:Actuate Therapeutics Inc: Employment; Epigene Therapeutics Inc: Consultancy, Other: leadership, stock/other ownership ; Novartis: Consultancy. Hochhaus:MSD: Research Funding; Novartis: Research Funding; BMS: Research Funding; Incyte: Research Funding; Pfizer: Research Funding.

Abstract: e19055 Background: Bosutinib (BOS) is approved for pts with Philadelphia chromosome-positive CML resistant/intolerant to prior therapy and newly diagnosed pts in chronic phase. Methods: The BYOND trial (NCT02228382) evaluated the efficacy and safety of BOS in 163 pts with CML resistant/intolerant to prior tyrosine kinase inhibitors (TKIs; Gambacorti-Passerini et al, Blood, 2021). We report a sub-analysis of 48 pts treated with 2 (3L) and 3 (4L) prior TKIs, categorized by resistance/intolerance to the last received TKI. This sub-analysis is based on the final Nov 23, 2020 database lock. Results: There were 18 and 30 pts resistant or intolerant to the last TKI who entered the study without complete cytogenetic response (CCyR) or major molecular response (MMR), respectively. Median (range) treatment duration was 10.6 mo (1.6–48.5) vs 28.3 mo (0.2–48.6) and median (range) dose intensity was 447.1 mg/d (131.3–520.4) vs 288.8 mg/d (79.7–500.0) for resistant vs intolerant pts. Prior TKIs included imatinib (88.9% vs 100.0%), dasatinib (88.9% vs 83.3%), and nilotinib (66.7% vs 63.3%) for resistant vs intolerant pts. Overall, 61.1% vs 66.7% of resistant vs intolerant pts discontinued BOS, mostly commonly due to adverse events (AEs) in 27.8% vs 16.7% pts; 16.7% vs 6.7% discontinued BOS due to insufficient clinical response. Rates of CCyR/MMR are shown in the table. Among responders (resistant vs intolerant pts), median (range) time to CCyR was 5.1 mo (2.8–8.8) vs 3.0 mo (2.7–6.1); median (range) time to MMR was 5.8 mo (2.8–9.4) vs 3.2 mo (2.8–9.3). In resistant vs intolerant pts, any grade treatment-emergent AEs (TEAEs) were reported by 100.0% vs 96.7% pts; grade 3/4 TEAEs were reported by 72.2% vs 83.3% pts. Grade 3/4 TEAEs 〉 10% in resistant pts were thrombocytopenia (22.2%) and neutropenia (11.1%), and in intolerant pts were increased alanine aminotransferase (26.7%), diarrhea (23.3%), pleural effusion (13.3%), and rash (13.3%). Conclusions: This sub-analysis of resistant/intolerant pts without baseline CCyR or MMR shows BOS was active in heavily pretreated pts with resistance/intolerance to the last TKI. Despite a difference between resistant/intolerant pts, efficacy outcomes, though lower than the overall BYOND population, are encouraging, and safety was generally consistent with previous reports. Clinical trial information: NCT02228382. [Table: see text]