14.1 Adult Patients with Newly-Diagnosed CP Ph+ CML

The efficacy of BOSULIF in patients with newly-diagnosed chronic phase Ph+ CML was evaluated in the Bosutinib trial in First-line chrOnic myelogenous leukemia tREatment (BFORE) Trial: "A Multicenter Phase 3, Open-Label Study of Bosutinib Versus Imatinib in Adult Patients With Newly Diagnosed Chronic Phase Chronic Myelogenous Leukemia" [NCT02130557].

The BFORE Trial is a 2-arm, open-label, randomized, multicenter trial conducted to investigate the efficacy and safety of BOSULIF 400 mg once daily alone compared with imatinib 400 mg once daily alone in adult patients with newly-diagnosed CP Ph+ CML. The trial randomized 536 patients (268 in each arm) with Ph+ or Ph- newly-diagnosed CP CML (intent-to-treat [ITT] population) including 487 patients with Ph+ CML harboring b2a2 and/or b3a2 transcripts at baseline and baseline BCR-ABL copies >0 (modified intent-to-treat [mITT] population). Randomization was stratified by Sokal score and geographical region. All patients are being treated and/or followed for up to 5 years (240 weeks). Efficacy was evaluated in the mITT population. The major efficacy outcome measure was major molecular response (MMR) at 12 months (48 weeks) defined as ≤0.1% BCR-ABL ratio on international scale (corresponding to ≥3 log reduction from standardized baseline) with a minimum of 3000 ABL transcripts as assessed by the central laboratory. Additional efficacy outcomes included CCyR by 12 months, defined as the absence of Ph+ metaphases in chromosome banding analysis of ≥20 metaphases derived from bone marrow aspirate or MMR if an adequate cytogenetic assessment was unavailable and MMR by 18 months (72 weeks).

In the mITT population in this study, 57% of patients were males, 78% were Caucasian, and 19% were 65 years or older. The median age was 53 years. At baseline, the distribution of Sokal risk scores was similar in bosutinib and imatinib-treated patients (low risk: 35% and 39%; intermediate risk: 44% and 38%; high risk: 22% and 22%, respectively). After a minimum of 12 months follow-up, 78% of the 246 bosutinib-treated patients and 72% of the 239 imatinib-treated patients were still receiving treatment and with a minimum of 60 months of follow-up, 60% and 60% of patients, respectively, were still receiving treatment. The median treatment duration was 55.1 months for BOSULIF and 55.0 months for imatinib.

The efficacy results from the BFORE trial are summarized in Table 13.

The MMR rate at Month 12 for all randomized patients (ITT population) was consistent with the mITT population (47% [95% CI: 41, 53] in the bosutinib treatment group and 36% [95% CI: 30, 42] in the imatinib treatment group; odds ratio of 1.57 [95% CI: 1.10, 2.22]). MMR by Month 60 (Week 240) in the mITT population was 74% (95% CI: 69, 80) in the bosutinib treatment group and 66% (95% CI: 60, 72) in the imatinib treatment group; odds ratio of 1.52 (95% CI: 1.02, 2.25). MMR by Month 60 in the ITT population was also consistent with the mITT population (1.57 [95% CI: 1.08, 2.28]).

After 60 months of follow-up, the median time to MMR in responders was 9.0 months for bosutinib and 11.9 months for imatinib.

By 60 months, the MMR rates in each Sokal risk group for the bosutinib and imatinib-treated patients, respectively, were 78% and 72% for low risk, 74% and 67% for intermediate risk and 68% and 52% for high risk.

After 60 months of follow-up, 6 (2%) bosutinib patients and 7 (3%) imatinib patients transformed to AP CML or BP CML while on treatment.

At 60 months, the estimated overall survival rate was 95% (95% CI: 91, 97) in the bosutinib group and 94% (95% CI: 90, 96) in the imatinib group.

14.2 Adult Patients with Imatinib-Resistant or -Intolerant Ph+ CP, AP, and BP CML

Study 200 (NCT00261846), a single-arm, open-label, multicenter study in patients with CML who were resistant or intolerant to prior therapy was conducted to evaluate the efficacy and safety of BOSULIF 500 mg once daily in patients with imatinib-resistant or -intolerant CML with separate cohorts for CP, AP, and BP disease previously treated with 1 prior TKI (imatinib) or more than 1 TKI (imatinib followed by dasatinib and/or nilotinib). The definition of imatinib resistance included (1) failure to achieve or maintain any hematologic improvement within 4 weeks; (2) failure to achieve a CHR by 3 months, cytogenetic response by 6 months or major cytogenetic response (MCyR) by 12 months; (3) progression of disease after a previous cytogenetic or hematologic response; or (4) presence of a genetic mutation in the BCR-ABL gene associated with imatinib resistance. Imatinib intolerance was defined as inability to tolerate imatinib due to toxicity, or progression on imatinib and inability to receive a higher dose due to toxicity. The definitions of resistance and intolerance to both dasatinib and nilotinib were similar to those for imatinib. The protocol was amended to exclude patients with a known history of the T315I mutation after 396 patients were enrolled in the trial.

The efficacy endpoints for patients with CP CML previously treated with 1 prior TKI (imatinib) were the rate of attaining MCyR by Week 24 and the duration of MCyR. The efficacy endpoints for patients with CP CML previously treated with both imatinib and at least 1 additional TKI were the cumulative rate of attaining MCyR by Week 24 and the duration of MCyR. The efficacy endpoints for patients with previously treated AP and BP CML were confirmed CHR and overall hematologic response (OHR).

The study enrolled 546 patients with CP, AP or BP CML. Of the total patient population 73% were imatinib resistant and 27% were imatinib intolerant. In this trial, 53% of patients were males, 65% were Caucasian, and 20% were 65 years old or older. Of the 546 treated patients, 506 were considered evaluable for cytogenetic or hematologic efficacy assessment. Patients were evaluable for efficacy if they had received at least 1 dose of BOSULIF and had a valid baseline efficacy assessment. Among evaluable patients, there were 262 patients with CP CML previously treated with 1 prior TKI (imatinib), 112 patients with CP CML previously treated with both imatinib and at least 1 additional TKI, and 132 patients with advanced phase CML previously treated with at least 1 TKI.

Median duration of BOSULIF treatment was 26 months in patients with CP CML previously treated with 1 TKI (imatinib), 9 months in patients with CP CML previously treated with imatinib and at least 1 additional TKI, 10 months in patients with AP CML previously treated with at least imatinib, and 3 months in patients with BP CML previously treated with at least imatinib.

The 24 week efficacy and MCyR at any time results are summarized in Table 14.

The long-term follow-up data analysis was based on a minimum of 60 months for patients with CP CML treated with 1 prior TKI (imatinib) and a minimum of 48 months for patients with CP CML treated with imatinib and at least 1 additional TKI. For the 59.5% of patients with CP CML treated with 1 prior TKI (imatinib) who achieved a MCyR at any time, the median duration of MCyR was not reached. Among these patients, 65.4% and 42.9% had a MCyR lasting at least 18 and 54 months, respectively. For the 40.2% of patients with CP CML treated with imatinib and at least 1 additional TKI who achieved a MCyR at any time, the median duration of MCyR was not reached. Among these patients, 64.4% and 35.6% had a MCyR lasting at least 9 and 42 months, respectively. Of the 403 treated patients with CP CML, 20 patients had confirmed disease transformation to AP or BP while on treatment with BOSULIF.

The 48-week efficacy results in patients with accelerated and blast phases CML previously treated with at least imatinib are summarized in Table 15.

The long-term follow-up data analysis was based on a minimum of 48 months for patients with AP CML and BP CML. Of the 79 treated patients with AP CML, 3 patients had confirmed disease transformation to BP while on BOSULIF treatment.

14.3 Pediatric Patients with Newly-Diagnosed CP Ph+ CML or with CP Ph+ CML with Resistance or Intolerance to Prior Therapy

The efficacy of BOSULIF in pediatric patients with newly-diagnosed (ND) chronic phase (CP) Ph+ CML and patients with resistant/intolerant (R/I) CP Ph+ CML was evaluated in the BCHILD trial [NCT04258943].

The BCHILD trial is a multicenter, non-randomized, open-label study conducted to identify a recommended dose of bosutinib administered orally once daily in pediatric patients with ND CP Ph+ CML and pediatric patients with R/I CP Ph+ CML who have received at least one prior TKI therapy, to estimate the safety and tolerability and efficacy, and to evaluate the PK of bosutinib in this patient population. The study enrolled 28 patients with R/I CP Ph+ CML treated with BOSULIF at 300 mg/m2 to 400 mg/m2 orally once daily, and 21 patients with ND CP Ph+ CML treated at 300 mg/m2 orally once daily. Efficacy outcomes included CCyR (defined as the absence of Ph+ metaphases in chromosome banding analysis of ≥20 metaphases, or <1% BCR-ABL1–positive nuclei of at least 200 peripheral blood interphase nuclei analyzed by Fluorescence In Situ Hybridization (FISH), or MMR if an adequate cytogenetic assessment was unavailable), MCyR (defined as CCyR or partial cytogenetic response of 1% to 35% Ph+ metaphases), and MMR (defined as ≤0.1% BCR-ABL ratio on international scale [IS]) at any time on study.

Patients with ND CP Ph+ CML had a median age of 14 years (range 5 to 17 years); 68% were male; 81% were White, 14% were Black/African American, and 5% were race not reported.

The major (MCyR) and complete (CCyR) cytogenetic responses among patients with ND CP Ph+ CML were 76.2% (95% CI: 52.8, 91.8) and 71.4% (95% CI: 47.8, 88.7), respectively. The MMR among patients with ND CP Ph+ CML was 28.6% (95% CI: 11.3, 52.3). The median duration of follow-up was 14.2 months (range: 1.1, 26.3 months) in patients with ND CP CML.

Patients with R/I CP Ph+ CML included n=6 treated at 300 mg/m2 (0.75 times the recommended dose), n=11 treated at 350 mg/m2 (0.875 times the recommended dose), and n=11 at 400 mg/m2. Overall (n=28), patients had a median age of 11.5 years (range: 1 to 17 years); 57% were male; 43% were White, 7% were Black/African American, 14% were Asian, and 36% were race not reported.

The major (MCyR) and complete (CCyR) cytogenetic responses among patients with R/I CP Ph+ CML were 82.1% (95% CI: 63.1, 93.9) and 78.6% (95% CI: 59.0, 91.7), respectively. The MMR among patients with R/I CP Ph+ CML was 50.0% (95% CI: 30.6, 69.4). The MR4.5 (defined as BCR-ABL/ABL IS ≤ 0.0032%) was 17.9% (95% CI: 6.1, 36.9). Among 14 patients who achieved MMR, two patients lost MMR after 13.6 months and 24.7 months on treatment. The median duration of follow-up for overall survival was 23.2 months (range: 1.0, 61.5 months) in patients with R/I CP Ph+ CML.