12 CLINICAL PHARMACOLOGY
12.1 Mechanism of Action
Bosutinib is a TKI. Bosutinib inhibits the BCR-ABL kinase that promotes CML; it is also an inhibitor of Src-family kinases including Src, Lyn, and Hck. Bosutinib inhibited 16 of 18 imatinib-resistant forms of BCR-ABL kinase expressed in murine myeloid cell lines. Bosutinib did not inhibit the T315I and V299L mutant cells.
12.2 Pharmacodynamics
Based on the exposure response analyses for efficacy, a relationship between drug exposure and a greater likelihood of response was observed in clinical studies. Based on the exposure response analyses for safety, a relationship between drug exposure and a greater likelihood of safety events was observed in clinical studies.
12.3 Pharmacokinetics
The bosutinib pharmacokinetics following oral dosing was assessed with food, unless otherwise specified.
Bosutinib exhibits dose proportional increases in AUC and Cmax over the oral dose range of 200 to 800 mg (0.33 to 1.3 times the maximum approved recommended dosage of 600 mg). The mean (standard deviation [SD]) Cmax was 146 (20) ng/mL and the mean (SD) AUC was 2720 (442) ng∙h/mL following multiple oral doses of BOSULIF 400 mg in patients with CML; Cmax was 200 (12) ng/mL and AUC was 3650 (425) ng∙h/mL following multiple oral doses of BOSULIF 500 mg in patients with CML.
Absorption
Following administration of a single oral dose of BOSULIF 500 mg with food in patients with CML, the median (minimum, maximum) time-to-peak concentration (tmax) was 6.0 (6.0, 6.0) hours. The absolute bioavailability was 34% in healthy subjects.
Distribution
Following a single intravenous dose of bosutinib 120 mg (0.2 times the maximum approved recommended oral dosage of 600 mg) in healthy subjects, bosutinib had a mean (SD) volume of distribution of 2441 (796) L. The mean (SD) apparent volume of distribution after an oral dose of 500 mg of BOSULIF to patients with CML was 6080 (1230) L. Protein binding of bosutinib is 94% in vitro and 96% ex vivo, and is independent of concentration.
Elimination
Following a single intravenous dose of bosutinib 120 mg (0.2 times the maximum approved recommended oral dosage of 600 mg), the mean (SD) terminal phase elimination half-life (t½) was 35.5 (8.5) hours, and the mean (SD) clearance (Cl) was 63.6 (14.1) L/h. Following a single oral dose of BOSULIF in patients with CML, the mean (SD) t½ was 22.5 (1.7) hours, and the mean (SD) Cl was 189 (48) L/h.
Specific Populations
Patients with Renal Impairment
Following a single oral dose of BOSULIF 200 mg (0.33 times the maximum approved recommended dosage of 600 mg), bosutinib AUC increased 1.4-fold in subjects with moderate renal impairment (CLcr: 30 to 50 mL/min, estimated by Cockcroft-Gault (C-G)) and increased 1.6-fold in subjects with severe renal impairment (CLcr less than 30 mL/min) compared to subjects with normal renal function (CLcr > 80 mL/min, C-G). No clinically significant difference in the pharmacokinetics of bosutinib was observed in subjects with mild renal impairment (CLcr: 51 to 80 mL/min, C-G).
Patients with Hepatic Impairment
Following a single oral dose of BOSULIF 200 mg (0.33 times the maximum approved recommended dosage of 600 mg), bosutinib Cmax increased 2.4-fold, 2-fold, and 1.5-fold, and AUC increased 2.3-fold, 2-fold, and 1.9-fold in hepatic impairment Child-Pugh A, B, and C, respectively.
Drug Interaction Studies
Clinical Studies
The following interactions were evaluated in crossover studies of healthy subjects, unless otherwise specified.
Strong and Moderate CYP3A Inhibitors
A single oral dose of BOSULIF 100 mg (0.17 times the maximum approved recommended dosage) was administered alone or following multiple daily doses of 400 mg ketoconazole (a strong CYP3A inhibitor) without food. Ketoconazole increased bosutinib Cmax and AUC 5.2-fold and 8.6-fold, respectively.
A single oral dose of BOSULIF 500 mg was administered alone or in combination with 125 mg aprepitant (a moderate CYP3A inhibitor) with food. Aprepitant increased bosutinib Cmax 1.5-fold and AUC 2.0-fold.
Strong CYP3A Inducers
A single dose of BOSULIF 500 mg was administered alone or following multiple daily doses of 600 mg rifampin with food. Rifampin decreased bosutinib Cmax by 86% and AUC by 94%.
Proton Pump Inhibitors
BOSULIF displays pH-dependent aqueous solubility, in vitro. A single oral dose of BOSULIF 400 mg was administered alone or following multiple oral doses of lansoprazole 60 mg without food. Lansoprazole decreased bosutinib Cmax by 46% and AUC by 26%.
P-gp Substrates
A single oral dose of 500 mg BOSULIF was administered in combination with a single oral dose of 150 mg dabigatran etexilate mesylate (a P-glycoprotein (P-gp) substrate). No clinically significant difference in the pharmacokinetics of dabigatran was observed following bosutinib administration.
In Vitro Studies
Bosutinib Effect on Transporters
Bosutinib may have the potential to inhibit breast cancer resistance protein (BCRP) in the gastrointestinal tract but has a low potential to inhibit BCRP, systemically, or organic anion transporting polypeptide (OATP)1B1, OATP1B3, organic anion transporter (OAT)1, OAT3, organic cation transporter (OCT)1, and OCT2 at clinically relevant concentrations.