CLINICAL PHARMACOLOGY
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
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 Ã ULN with any AST) and 5
patients had moderate hepatic impairment (total bilirubin > 1.5 to 3 Ã ULN
and any AST), no effects on pharmacokinetics of dacomitinib were observed. The
effect of severe hepatic impairment (total bilirubin > 3 to 10 Ã ULN and any
AST) on dacomitinib pharmacokinetics is unknown [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