Absolute Bioavailability of Bosutinib in Healthy Subjects From an Open-Label, Randomized, 2-Period Crossover Study

This study evaluated the absolute bioavailability of bosutinib and assessed its safety and tolerability after single-dose oral and intravenous administration. In this phase 1 open-label, 2-sequence, 2-period crossover study, healthy, fed subjects aged 18-55 years were randomized to 1 of 2 treatment sequences (n = 7/sequence): oral bosutinib (100 mg × 5) followed by intravenous bosutinib (120 mg in approximately 240 mL over 1 hour), with a ≥14-day washout, or intravenous bosutinib and then oral bosutinib. Results of plasma pharmacokinetics analyses demonstrated that exposure to intravenous bosutinib was 3-fold higher than for oral bosutinib (16.2 and 5.5 ng·h/mL/mg, respectively), and mean terminal half-life was similar (35.5 and 31.7 hours). The ratio of adjusted geometric means (90%CI) for the dose-normalized area under the plasma concentration-time profile (AUC_0-∞ /D) was 33.85% (30.65%-37.38%). Most treatment-emergent adverse events (AEs) were mild in severity. Gastrointestinal (GI) AEs occurred in 9 of 13 subjects given oral bosutinib, whereas no subjects given intravenous bosutinib experienced GI AEs, suggesting bosutinib present in the GI tract had an effect. Bosutinib exhibited an absolute bioavailability of 33.85% based on the ratio of AUC_0-∞ /D. Both oral and intravenous bosutinib were safe and well tolerated in healthy, fed adult subjects.