Clinical Pharmacology for Vizimpro
Mechanism Of Action
Dacomitinib is an irreversible inhibitor of the kinase activity of the human EGFR family (EGFR/HER1, HER2, and HER4) and certain EGFR activating mutations (exon 19 deletion or the exon 21 L858R substitution mutation). In vitro dacomitinib also inhibited the activity of DDR1, EPHA6, LCK, DDR2, and MNK1 at clinically relevant concentrations.
Dacomitinib demonstrated dose-dependent inhibition of EGFR and HER2 autophosphorylation and tumor growth in mice bearing subcutaneously implanted human tumor xenografts driven by HER family targets including mutated EGFR. Dacomitinib also exhibited antitumor activity in orally-dosed mice bearing intracranial human tumor xenografts driven by EGFR amplifications.
Pharmacodynamics
Cardiac Electrophysiology
The effect of dacomitinib on the QT interval corrected for heart rate (QTc) was evaluated using time-matched electrocardiograms (ECGs) evaluating the change from baseline and corresponding pharmacokinetic data in 32 patients with advanced NSCLC. Dacomitinib had no large effect on QTc (i.e., >20 ms) at maximum dacomitinib concentrations achieved with VIZIMPRO 45 mg orally once daily.
Exposure-Response Relationships
Higher exposures, across the range of exposures with the recommended dose of 45 mg daily, correlated with an increased probability of Grade ≥3 adverse events, specifically dermatologic toxicities and diarrhea.
Pharmacokinetics
The maximum dacomitinib plasma concentration (Cmax) and AUC at steady state increased proportionally over the dose range of VIZIMPRO 2 mg to 60 mg orally once daily (0.04 to 1.3 times the recommended dose) across dacomitinib studies in patients with cancer. At a dose of 45 mg orally once daily, the geometric mean [coefficient of variation (CV%)] Cmax was 108 ng/mL (35%) and the AUC0-24h was 2213 ng•h/mL (35%) at steady state in a dose-finding clinical study conducted in patients with solid tumors. Steady state was achieved within 14 days following repeated dosing and the estimated geometric mean (CV%) accumulation ratio was 5.7 (28%) based on AUC.
Absorption
The mean absolute bioavailability of dacomitinib is 80% after oral administration. The median dacomitinib time to reach maximum concentration (Tmax) occurred at approximately 6.0 hours (range 2.0 to 24 hours) after a single oral dose of VIZIMPRO 45 mg in patients with cancer.
Effect of Food
Administration of VIZIMPRO with a high-fat, high-calorie meal (approximately 800 to 1000 calories with 150, 250, and 500 to 600 calories from protein, carbohydrate and fat, respectively) had no clinically meaningful effect on dacomitinib pharmacokinetics.
Distribution
The geometric mean (CV%) volume of distribution of dacomitinib (Vss) was 1889 L (18%). In vitro binding of dacomitinib to human plasma proteins is approximately 98% and is independent of drug concentrations from 250 ng/mL to 1000 ng/mL.
Elimination
Following a single 45 mg oral dose of VIZIMPRO in patients with cancer, the mean (CV%) plasma half-life of dacomitinib was 70 hours (21%), and the geometric mean (CV%) apparent plasma clearance of dacomitinib was 24.9 L/h (36%).
Metabolism
Hepatic metabolism is the main route of clearance of dacomitinib, with oxidation and glutathione conjugation as the major pathways. Following oral administration of a single 45 mg dose of [14C] dacomitinib, the most abundant circulating metabolite was O-desmethyl dacomitinib, which had similar in vitro pharmacologic activity as dacomitinib. 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
No clinically significant differences in the pharmacokinetics of dacomitinib were observed in subjects with mild, moderate or severe hepatic impairment (Child-Pugh A, B or C) [see Use In Specific Populations].
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 and DRUG INTERACTIONS].
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 and DRUG INTERACTIONS].
The effect of H2 receptor antagonists on dacomitinib pharmacokinetics has not been studied [see DOSAGE AND ADMINISTRATION and DRUG INTERACTIONS].
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].
In Vitro Studies
Effect of Dacomitinib and O-desmethyl Dacomitinib on CYP Enzymes
Dacomitinib and its metabolite O-desmethyl dacomitinib do not inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, or CYP3A4/5. Dacomitinib does not induce CYP1A2, CYP2B6, or CYP3A4.
Effect of Dacomitinib on Uridine 5’ diphospho-glucuronosyltransferase (UGT) Enzymes
Dacomitinib inhibits UGT1A1. Dacomitinib does not inhibit UGT1A4, UGT1A6, UGT1A9, UGT2B7, or UGT2B15.
Effect of Dacomitinib on Transporter Systems
Dacomitinib is a substrate for the membrane transport protein P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP). Dacomitinib inhibits P-gp, BCRP, and organic cation transporter (OCT)1. Dacomitinib does not inhibit organic anion transporters (OAT)1 and OAT3, OCT2, organic anion transporting polypeptide (OATP)1B1, and OATP1B3.
Clinical Studies
The efficacy of VIZIMPRO was demonstrated in a randomized, multicenter, multinational, open-label study (ARCHER 1050; [NCT01774721]). Patients were required to have unresectable, metastatic NSCLC with no prior therapy for metastatic disease or recurrent disease with a minimum of 12 months disease-free after completion of systemic therapy; an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1; EGFR exon 19 deletion or exon 21 L858R substitution mutations. EGFR mutation status was prospectively determined by local laboratory or commercially available tests (e.g., therascreen® EGFR RGQ PCR and cobas® EGFR Mutation Test).
Patients were randomized (1:1) to receive VIZIMPRO 45 mg orally once daily or gefitinib 250 mg orally once daily until disease progression or unacceptable toxicity. Randomization was stratified by region (Japanese versus mainland Chinese versus other East Asian versus non-East Asian), and EGFR mutation status (exon 19 deletions versus exon 21 L858R substitution mutation). The major efficacy outcome measure was progression-free survival (PFS) as determined by blinded Independent Radiologic Central (IRC) review per RECIST v1.1. Additional efficacy outcome measures were overall response rate (ORR), duration of response (DoR), and overall survival (OS).
A total of 452 patients were randomized to receive VIZIMPRO (N=227) or gefitinib (N=225). The demographic characteristics were 60% female; median age 62 years (range: 28 to 87), with 40% aged 65 years and older; and 23% White, 77% Asian, and less than 1% Black. Prognostic and tumor characteristics were ECOG performance status 0 (30%) or 1 (70%); 59% with exon 19 deletion and 41% with exon 21 L858R substitution; Stage IIIB (8%) and Stage IV (92%); 64% were never smokers; and 1% received prior adjuvant or neoadjuvant therapy.
ARCHER 1050 demonstrated a statistically significant improvement in PFS as determined by the IRC. Results are summarized in Table 5 and Figures 1 and 2.
The hierarchical statistical testing order was PFS followed by ORR and then OS. No formal testing of OS was conducted since the formal comparison of ORR was not statistically significant.
Table 5. Efficacy Results in ARCHER 1050
| VIZIMPRO N=227 | Gefitinib N=225 |
| Progression-Free Survival (per IRC) |
| Number of patients with event, n (%) | 136 (59.9%) | 179 (79.6%) |
| Median PFS in months (95% CI) | 14.7 (11.1, 16.6) | 9.2 (9.1, 11.0) |
| HR (95% CI)a | 0.59 (0.47, 0.74) |
| p-valueb | <0.0001 |
| Overall Response Rate (per IRC) |
| Overall Response Rate % (95% CI) | 75% (69, 80) | 72% (65, 77) |
| p-valuec | 0.39 |
| Duration of Response in Responders (per IRC) |
| Median DoR in months (95% CI) | 14.8 (12.0, 17.4) | 8.3 (7.4, 9.2) |
CI=confidence interval; DoR=duration of response; HR=hazard ratio; IRC=Independent Radiologic Central; N/n=total number; PFS=progression-free survival. a. From stratified Cox Regression. b. Based on the stratified log-rank test. c. Based on the stratified Cochran-Mantel-Haenszel test. |
Figure 1. Kaplan-Meier Curve for PFS per IRC Review in ARCHER 1050
Figure 2. Kaplan-Meier Curve for OS in ARCHER 1050