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BOSULIF® (bosutinib) Clinical Studies

14 CLINICAL STUDIES

14.1 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. Efficacy was evaluated in the mITT population. The major efficacy outcome measure was MMR at 12 months 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.

In the mITT population in this study, 57% of patients were males, 77% were Caucasian, and 19% were 65 years or older. The median age was 53 years. After a minimum of 12 months of follow-up, 77.6% of the 246 bosutinib-treated patients and 72.4% of the 239 imatinib-treated patients were still receiving treatment. The median treatment duration was 14.3 months for BOSULIF and 13.8 months for imatinib.

The efficacy results from the BFORE trial are summarized in Table 8.

Table 8: Summary of Major Molecular Response (MMR) at Month 12 and Complete Cytogenetic Response (CCyR) by Month 12, by Treatment Group in the Modified Intent-to-Treat (mITT) Population
ResponseBosutinib
N=246
n (%)
Imatinib
N=241
n (%)
2-sided p-value
Abbreviations: CCyR=complete cytogenetic response; CI=confidence interval; CMH=Cochran-Mantel-Haenszel; MMR=major molecular response; N/n=number of patients.
*
derived from CMH test stratified by Geographical region and Sokal score at randomization.
Major Molecular Response at Month 12
  MMR116 (47.2)89 (36.9)0.0200*
  (95% CI)(40.9, 53.4)(30.8, 43.0)
Complete Cytogenetic Response by Month 12
  CCyR190 (77.2)160 (66.4)0.0075*
  (95% CI)(72.0, 82.5)(60.4, 72.4)

The MMR rate at Month 12 for all randomized patients (ITT population) was consistent with the mITT population (46.6% [95% CI: 40.7, 52.6] in the bosutinib treatment group and 36.2% [95% CI: 30.4, 41.9] in the imatinib treatment group; odds ratio of 1.57 [95% CI: 1.10, 2.22]). After a minimum of 12 months of follow-up, 5 bosutinib patients and 7 imatinib patients transformed to AP CML or BP CML while on treatment.

14.2 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 9.

Table 9: Efficacy Results in Patients with Ph+ CP CML With Resistance to or Intolerance to Imatinib
Prior Treatment With Imatinib Only
(N=262 evaluable)
n (%)
Prior Treatment With Imatinib and Dasatinib or Nilotinib
(N=112 evaluable)
n (%)
Abbreviations: CI=confidence interval; CML=chronic myelogenous leukemia; CP=chronic phase; MCyR=major cytogenetic response; N/n=number of patients; Ph+=Philadelphia chromosome positive.
By Week 24
  MCyR105 (40.1)29 (25.9)
  (95% CI)(34.1, 46.3)(18.1, 35.0)
MCyR any time156 (59.5)45 (40.2)
(53.3, 65.5)(31.0, 49.9)

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 10.

Table 10: Efficacy Results in Patients With Accelerated Phase and Blast Phase CML Previously Treated With at Least Imatinib
AP CML
(N=72 evaluable)
n (%)
BP CML
(N=60 evaluable)
n (%)
Abbreviations: AP=accelerated phase; BP=blast phase; CHR=complete hematologic response; CI=confidence interval; CML=chronic myelogenous leukemia; CI=confidence interval, OHR=overall hematologic response, CHR=complete hematologic response, N/n=number of patients
*
Overall hematologic response (OHR) = major hematologic response (complete hematologic response + no evidence of leukemia) or return to chronic phase (RCP). All responses were confirmed after 4 weeks. Complete hematologic response (CHR) for AP and BP CML: WBC less than or equal to institutional ULN, platelets greater than or equal to 100,000/mm3 and less than 450,000/mm3, absolute neutrophil count (ANC) greater than or equal to 1.0×109 /L, no blasts or promyelocytes in peripheral blood, less than 5% myelocytes + metamyelocytes in bone marrow, less than 20% basophils in peripheral blood, and no extramedullary involvement. No evidence of leukemia (NEL): Meets all other criteria for CHR except may have thrombocytopenia (platelets greater than or equal to 20,000/mm3 and less than 100,000/mm3) and/or neutropenia (ANC greater than or equal to 0.5×109 /L and less than 1.0×109 /L). Return to chronic phase (RCP) = disappearance of features defining accelerated or blast phases but still in chronic phase.
CHR* by Week 4822 (30.6)10 (16.7)
  (95% CI)(20.2, 42.5)(8.3, 28.5)
OHR* by Week 4841 (56.9)17 (28.3)
  (95% CI)(44.7, 68.6)(17.5, 41.4)

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.

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