CLINICAL PHARMACOLOGY
Mechanism Of Action
The mechanism of action of pirfenidone in the treatment of IPF has not been established.
Pharmacodynamics
Cardiac Electrophysiology
The effect of ESBRIET on QT interval was evaluated in a randomized, placebo, and positive
controlled parallel study in 160 healthy adult volunteers. Volunteers received ESBRIET
2403 mg/day (recommended dose) and 4005 mg/day (1.6 times recommended dose) or
placebo for 10 days or a single dose of 400 mg moxifloxacin (active control).
Relative to placebo, the maximum mean change from baseline in study-specific QT interval
was 3.2 milliseconds (ms) and 2.2 ms for ESBRIET 2403 mg/day and 4005 mg/day,
respectively. No volunteer had a QTc interval greater than 480 ms or change from baseline
greater than 60 ms. Although there was no evidence that ESBRIET prolonged the QTc
interval in this study, a definitive conclusion may not be drawn as the positive control
(moxifloxacin) did not perform as expected in this study, and ESBRIET at 4005 mg/day
(1.7 times the maximum recommended dose) did not cover the maximum pirfenidone exposure
increase with co-administration of fluvoxamine, a strong CYP1A2 inhibitor.
Pharmacokinetics
Absorption
After single oral-dose administration of 801 mg ESBRIET (three 267 mg capsules), the
maximum observed plasma concentration (Cmax) was achieved between 30 minutes and
4 hours (median time of 0.5 hours). Food decreased the rate and extent of absorption.
Median Tmax increased from 0.5 hours to 3 hours with food. Maximum plasma
concentrations (Cmax) and AUC0-inf decreased by approximately 49% and 16% with food,
respectively.
Bioequivalence was demonstrated in the fasted state when comparing the 801 mg tablet to
three 267 mg capsules. The effect of food on pirfenidone exposure was consistent between
the tablet and capsule formulations.
A reduced incidence of adverse reactions was observed in the fed group when compared to
the fasted group. In controlled studies with IPF patients, ESBRIET was taken with food [see DOSAGE AND ADMINISTRATION and Clinical Studies].
The absolute bioavailability of pirfenidone has not been determined in humans.
Distribution
ESBRIET binds to human plasma proteins, primarily to serum albumin, in a concentrationindependent
manner over the range of concentrations observed in clinical trials. The overall
mean binding was 58% at concentrations observed in clinical studies (1 to 10 μg/mL). Mean
apparent oral volume of distribution is approximately 59 to 71 liters.
Metabolism
In vitro profiling studies in hepatocytes and liver microsomes have shown that ESBRIET is
primarily metabolized in the liver by CYP1A2 and multiple other CYPs (CYP2C9, 2C19,
2D6, and 2E1). Oral administration of ESBRIET results in the formation of four metabolites.
In humans, only pirfenidone and 5-carboxy-pirfenidone are present in plasma in significant
quantities. The mean metabolite-to-parent ratio ranged from approximately 0.6 to 0.7.
No formal radiolabeled studies have assessed the metabolism of pirfenidone in humans. In
vitro data suggests that metabolites are not expected to be pharmacologically active at
observed metabolite concentrations.
Elimination
The mean terminal half-life is approximately 3 hours in healthy subjects. Pirfenidone is
excreted predominantly as metabolite 5-carboxy-pirfenidone, mainly in the urine
(approximately 80% of the dose). The majority of ESBRIET was excreted as the 5-carboxy
metabolite (approximately 99.6% of that recovered).
Specific Populations
Hepatic Impairment
The pharmacokinetics of ESBRIET and the 5-carboxy-pirfenidone metabolite were studied in
12 subjects with moderate hepatic impairment (Child Pugh Class B) and in 12 subjects with
normal hepatic function. Results showed that the mean exposure, AUC0-inf and Cmax of
pirfenidone increased approximately 1.6- and approximately 1.4-fold in subjects with
moderate hepatic impairment, respectively. The exposure of 5-carboxy-pirfenidone did not
change significantly in subjects with moderate hepatic impairment.
Renal Impairment
The pharmacokinetics of pirfenidone and the 5-carboxy-pirfenidone metabolite were studied
in 18 subjects with mild (CLcr 50 to 80 mL/min), moderate (CLcr 30 to 50 mL/min), and
severe (CLcr less than 30 mL/min) renal impairment (n=6/group) and in 6 subjects with
normal CLcr (greater than or equal to 80 mL/min) renal function. Results showed that
systemic exposure (AUC0-inf) to pirfenidone increased approximately 1.4, 1.5, and 1.2-fold in
subjects with mild, moderate and severe renal impairment, respectively. The corresponding
AUC0-inf of 5-carboxy-pirfenidone increased 1.7, 3.4, and 5.6-fold, although the change in the
patients with mild renal impairment was not statistically significant. The renal clearance of
5-carboxy-pirfenidone decreased significantly in patients with moderate to severe renal
impairment.
The pharmacokinetics and safety of ESBRIET has not been studied in subjects with endstage
renal disease requiring dialysis.
Geriatric
Results of population pharmacokinetic analysis suggest that no dosage adjustment is needed
in geriatric patients.
Gender
Results of population pharmacokinetic analysis of ESBRIET showed no significant
differences in pharmacokinetics between males and females.
Obesity
Results of population pharmacokinetic analysis showed that obesity (Body Mass Index
[BMI] greater than or equal to 30 kg/m2) has no significant effect on the pharmacokinetics of
ESBRIET.
Race
Population pharmacokinetic analysis showed that race has no significant effect on the
pharmacokinetics of pirfenidone.
Drug Interaction Studies
Cytochrome P450 1A2 Inhibitors
Pirfenidone is a substrate of cytochrome P450 1A2. In a single-dose drug interaction study
in 25 healthy nonsmokers and 25 smokers, ESBRIET was coadministered with fluvoxamine
(50 mg at bedtime for 3 days; 50 mg twice a day for 3 days, and 50 mg in the morning and
100 mg at bedtime for 4 days). An approximately 4-fold increase in exposure to pirfenidone
in nonsmokers and approximately 7-fold increase in exposure 1in smokers was observed.
In a single-dose drug interaction study in 27 healthy subjects, coadministration of 801 mg of
ESBRIET and 750 mg of ciprofloxacin (a moderate inhibitor of CYP1A2) on Day 6
(ciprofloxacin was dosed at 750 mg twice daily from Day 2 to Day 7) increased the exposure
to pirfenidone by 81%.
Cytochrome P450 1A2 Inducers
Following a single oral dose of 801 mg ESBRIET in 25 smokers and 25 healthy nonsmokers,
the systemic exposure in smokers was significantly lower compared to nonsmokers. AUC0-inf
and Cmax of pirfenidone in smokers were 46% and 68% of those in nonsmokers, respectively.
Inhibitory Effect Of Pirfenidone On P-Glycoprotein (Pgp)
The potential for pirfenidone to inhibit Pgp mediated transport of digoxin (5.0 μM) was
evaluated in the absence and presence of pirfenidone at concentrations ranging from 1 to
1000 μM in in vitro system. Pirfenidone showed weak inhibition (10 to 30%) of Pgp
facilitated digoxin B-A efflux at concentrations of 100 μM and above. Effect of pirfenidone
upon Pgp substrate pharmacokinetics and safety has not been evaluated in humans.
Inhibitory Effect Of Pirfenidone On CYP2C9, 2C19 Or 1A2, 2D6, 3A4
The potential for pirfenidone to inhibit CYP2C9, 2C19 or 1A2 was evaluated in vitro at
concentrations up to 1000 μM (approximately 10-fold the mean human Cmax). Pirfenidone
showed a concentration-dependent inhibition on CYP2C9, 2C19 or 1A2, 2D6, and 3A4. At
1000 μM, pirfenidone inhibits the activity of these enzymes by 30.4%, 27.5%, 34.1%, 21%,
and 9.6%, respectively. Effect of pirfenidone upon pharmacokinetics and safety of CYP2C9,
2C19, 1A2, 2D6, and 3A4 substrates has not been evaluated in humans.
Clinical Studies
The efficacy of ESBRIET was evaluated in patients with IPF in three phase 3, randomized,
double-blind, placebo-controlled, multicenter trials (Studies 1, 2, and 3).
Study 1 was a 52-week trial comparing ESBRIET 2403 mg/day (n=278) versus placebo
(n=277) in patients with IPF. Study 2 and Study 3 were nearly identical to each other in
design, with few exceptions, including an intermediate dose treatment arm in Study 2.
Study 2 compared treatment with either ESBRIET 2403 mg/day (n=174) or ESBRIET
1197 mg/day (n=87) to placebo (n=174), while Study 3 compared ESBRIET 2403 mg/day
(n=171) to placebo (n=173). Study drug was administered three times daily with food for a
minimum of 72 weeks. Patients continued on treatment until the last patient completed
72 weeks of treatment, which included observations to approximately 120 weeks of study
treatment. The primary endpoint was the change in percent predicted forced vital capacity
(%FVC) from baseline to study end, measured at 52 weeks in Study 1, and at 72 weeks in
Studies 2 and 3.
Studies 1, 2 and 3 enrolled adult patients who had a clinical and radiographic diagnosis of
IPF (with or without accompanying surgical lung biopsy), without evidence or suspicion of
an alternative diagnosis for interstitial lung disease. Eligible patients were to have %FVC
greater than or equal to 50% at baseline and a percent predicted diffusing capacity of the
lungs for carbon monoxide (%DLCO) greater than or equal to 30% (Study 1) or 35%
(Studies 2 and 3) at baseline. In all three trials, over 80% of patients completed study
treatment.
A total of 1247 patients with IPF were randomized to receive ESBRIET 2403 mg/day
(n=623) or placebo (n=624) in these three trials. Baseline characteristics were generally
balanced across treatment groups. The study population ranged from 40 to 80 years of age
(mean age 67 years). Most patients were male (74%), white (95%), and current or former
smokers (65%). Approximately 93% of patients met criteria for definite IPF on high
resolution computed tomography (HRCT). Baseline mean %FVC and %DLCO were 72%
and 46%, respectively. Approximately 15% subjects discontinued from each treatment
group.
Change From Baseline In Percent Predicted Forced Vital Capacity
In Study 1, the primary efficacy analysis for the change in %FVC from baseline to Week 52
demonstrated a statistically significant treatment effect of ESBRIET 2403 mg/day (n=278)
compared with placebo (n=277) using a rank ANCOVA with the lowest rank imputation for
missing data due to death. In Study 2, there was a statistically significant difference at
Week 72 for the change in %FVC from baseline. In Study 3, there was no statistically
significant difference at Week 72 for the change in %FVC from baseline.
Figure 1 presents the cumulative distribution for all cut-offs for the change from baseline in
%FVC at Week 52 for Study 1. For all categorical declines in lung function, the proportion
of patients declining was lower on ESBRIET than on placebo. Study 2 showed similar
results.
Figure 1. Cumulative Distribution of Patients by Change in Percent Predicted FVC
from Baseline to Week 52 (Study 1). The Dashed Lines Indicate ≥10%
Decline or ≥0% Decline.
Mean Change From Baseline In FVC (mL)
In Study 1, a reduction in the mean decline in FVC (in mL) was observed in patients
receiving ESBRIET 2403 mg/day (-235 mL) compared to placebo (-428 mL) (mean
treatment difference 193 mL) at Week 52 (see Figure 2). In Study 2, a reduction in the
decline in FVC volume was also observed in patients receiving ESBRIET 2403 mg/day
compared with placebo (mean treatment difference 157 mL) at Week 72. There was no
statistically significant difference in decline in FVC volume seen in Study 3.
Figure 2. Mean Change from Baseline in Forced Vital Capacity (Study 1)
Survival
Survival was evaluated for ESBRIET compared to placebo in Studies 1, 2, and 3 as an
exploratory analysis to support the primary endpoint (FVC). All-cause mortality was
assessed over the study duration and available follow-up period, irrespective of cause of
death and whether patients continued treatment. All-cause mortality did not show a
statistically significant difference (see Figure 3).
Figure 3. Kaplan-Meier Estimates of All-Cause Mortality at Vital Status – End of
Study: Studies 1, 2, and 3