b. The steady-state plasma trough concentration of O-desmethyl dacomitinib ranges from 7.4% to 19% of the parent. In vitro studies indicated that cytochrome P450 (CYP) 2D6 was the major isozyme involved in the formation of O-desmethyl dacomitinib, while CYP3A4 contributed to the formation of other minor oxidative metabolites.
Excretion
Following a single oral 45 mg dose of [14C] radiolabeled dacomitinib, 79% of the radioactivity was recovered in feces (20% as dacomitinib) and 3% in urine (<1% as dacomitinib).
Specific Populations
Patients with Renal Impairment
Based on population pharmacokinetic analyses, mild (60 mL/min ≤ CLcr <90 mL/min; N=590) and moderate (30 mL/min ≤ CLcr <60 mL/min; N=218) renal impairment did not alter dacomitinib pharmacokinetics, relative to the pharmacokinetics in patients with normal renal function (CLcr ≥90 mL/min; N=567). The pharmacokinetics of dacomitinib has not been adequately characterized in patients with severe renal impairment (CLcr <30 mL/min) (N=4) or studied in patients requiring hemodialysis.
Patients with Hepatic Impairment
In a dedicated hepatic impairment trial, following a single oral dose of 30 mg VIZIMPRO, dacomitinib exposure (AUCinf and Cmax) was unchanged in subjects with mild hepatic impairment (Child-Pugh A; N=8) and decreased by 15% and 20%, respectively in subjects with moderate hepatic impairment (Child-Pugh B; N=9) when compared to subjects with normal hepatic function (N=8). Based on this trial, mild and moderate hepatic impairment had no clinically important effects on pharmacokinetics of dacomitinib. In addition, based on a population pharmacokinetic analysis of 1381 patients, in which 158 patients had mild hepatic impairment (total bilirubin ≤ ULN and AST > ULN, or total bilirubin > 1 to 1.5 × ULN with any AST) and 5 patients had moderate hepatic impairment (total bilirubin > 1.5 to 3 × ULN and any AST), no effects on pharmacokinetics of dacomitinib were observed. The effect of severe hepatic impairment (total bilirubin > 3 to 10 × ULN and any AST) on dacomitinib pharmacokinetics is unknown [see Use in Specific Populations (8.7)].
Drug Interaction Studies
Clinical Studies
Effect of Acid-Reducing Agents on Dacomitinib
Coadministration of a single 45 mg dose of VIZIMPRO with multiple doses of rabeprazole (a proton pump inhibitor) decreased dacomitinib Cmax by 51% and AUC0–96h by 39% [see Dosage and Administration (2.4) and Drug Interactions (7.1)].
Coadministration of VIZIMPRO with a local antacid (Maalox® Maximum Strength, 400 mg/5 mL) did not cause clinically relevant changes dacomitinib concentrations [see Dosage and Administration (2.4) and Drug Interactions (7.1)].
The effect of H2 receptor antagonists on dacomitinib pharmacokinetics has not been studied [see Dosage and Administration (2.4) and Drug Interactions (7.1)].
Effect of Strong CYP2D6 Inhibitors on Dacomitinib
Coadministration of a single 45 mg dose of VIZIMPRO with multiple doses of paroxetine (a strong CYP2D6 inhibitor) in healthy subjects increased the total AUClast of dacomitinib plus its active metabolite (O-desmethyl dacomitinib) in plasma by approximately 6%, which is not considered clinically relevant.
Effect of Dacomitinib on CYP2D6 Substrates
Coadministration of a single 45 mg oral dose of VIZIMPRO increased dextromethorphan (a CYP2D6 substrate) Cmax by 9.7-fold and AUClast by 9.6-fold [see Drug Interactions (7.2 |
