CLINICAL PHARMACOLOGY
Mechanism Of Action
Fosaprepitant is a prodrug of
aprepitant and accordingly, its antiemetic effects are attributable to aprepitant.
Aprepitant is a selective
high-affinity antagonist of human substance P/neurokinin 1 (NK1) receptors.
Aprepitant has little or no affinity for serotonin (5-HT 3), dopamine, and
corticosteroid receptors, the targets of existing therapies for chemotherapy-induced
nausea and vomiting (CINV). Aprepitant has been shown in animal models to
inhibit emesis induced by cytotoxic chemotherapeutic agents, such as cisplatin,
via central actions. Animal and human Positron Emission Tomography (PET)
studies with aprepitant have shown that it crosses the blood brain barrier and
occupies brain NK 1 receptors. Animal and human studies show that aprepitant
augments the antiemetic activity of the 5-HT 3-receptor antagonist ondansetron
and the corticosteroid dexamethasone and inhibits both the acute and delayed
phases of cisplatin-induced emesis.
Pharmacodynamics
Cardiac Electrophysiology
In a randomized, double-blind,
positive-controlled, thorough QTc study, a single 200-mg dose of fosaprepitant
(approximately 1.3 times the recommended dose) had no effect on the QTc
interval.
Pharmacokinetics
Aprepitant after Fosaprepitant
Administration
Following administration of a
single intravenous 150-mg dose of fosaprepitant, a prodrug of aprepitant
administered as a 20-minute infusion to healthy subjects, the mean AUC 0-∞
of aprepitant was 37.4 (± 14.8) mcg•hr/mL and the mean maximal aprepitant
concentration (C max ) was 4.2 (± 1.2) mcg/mL. Plasma concentrations of
fosaprepitant are below the limits of quantification (10 ng/mL) within 30
minutes of the completion of infusion.
Distribution
Aprepitant is greater than 95%
bound to plasma proteins. The mean apparent volume of distribution at steady
state (Vd ss) was approximately 70 L in humans.
Aprepitant crosses the blood
brain barrier in humans [see Mechanism of Action].
Elimination
Metabolism
Fosaprepitant is converted to
aprepitant in in vitro incubations with human liver preparations and in S9
preparations from multiple other human tissues including kidney, lung and
ileum. Thus, it appears that the conversion of fosaprepitant to aprepitant can occur
in multiple extrahepatic tissues in addition to the liver.
Aprepitant undergoes extensive
metabolism. In vitro studies using human liver microsomes indicate that
aprepitant is metabolized primarily by CYP3A4 with minor metabolism by CYP1A2
and CYP2C19. Metabolism is largely via oxidation at the morpholine ring and its
side chains. No metabolism by CYP2D6, CYP2C9, or CYP2E1 was detected.
In healthy young adults,
aprepitant accounts for approximately 24% of the radioactivity in plasma over
72 hours following a single oral 300-mg dose of [14C]-aprepitant,
indicating a substantial presence of metabolites in the plasma. Seven
metabolites of aprepitant, which are only weakly active, have been identified
in human plasma.
Excretion
Following administration of a
single intravenous 100-mg dose of [14C]-fosaprepitant to healthy
subjects, 57% of the radioactivity was recovered in urine and 45% in feces.
Aprepitant is eliminated
primarily by metabolism; aprepitant is not renally excreted. The apparent
terminal half-life ranged from approximately 9 to 13 hours.
Specific Populations
Age: Geriatric Population
Following oral administration
of a single 125-mg dose of aprepitant on Day 1 and 80 mg once daily on Days 2
through 5, the AUC 0-24hr of aprepitant was 21% higher on Day 1 and 36% higher
on Day 5 in elderly (65 years and older) relative to younger adults. The C max was
10% higher on Day 1 and 24% higher on Day 5 in elderly relative to younger
adults. These differences are not considered clinically meaningful [see Use
in Specific Populations].
Sex
Following oral administration
of a single dose of aprepitant, ranging from 40 mg to 375 mg, the AUC 0-24hr and
Cmax are 14% and 22% higher in females as compared with males. The half-life of
aprepitant is 25% lower in females as compared with males and T max occurs at
approximately the same time. These differences are not considered clinically
meaningful.
Race/Ethnicity
Following oral administration
of a single dose of aprepitant, ranging from 40 mg to 375 mg, the AUC 0-24hr and
C max are approximately 42% and 29% higher in Hispanics as compared with
Caucasians. The AUC 0-24hr and C max were 62% and 41% higher in Asians as
compared to Caucasians. There was no difference in AUC 0-24hr or C max between
Caucasians and Blacks. These differences are not considered clinically
meaningful.
Renal Impairment
A single 240-mg oral dose of
aprepitant was administered to patients with severe renal impairment
(creatinine clearance less than 30 mL/min/1.73 m² as measured by
24-hour urinary creatinine clearance) and to patients with end stage renal
disease (ESRD) requiring hemodialysis.
In patients with severe renal
impairment, the AUC 0-∞ of total aprepitant (unbound and protein bound)
decreased by 21% and C max decreased by 32%, relative to healthy subjects
(creatinine clearance greater than 80 mL/min estimated by Cockcroft-Gault
method). In patients with ESRD undergoing hemodialysis, the AUC 0-∞ of
total aprepitant decreased by 42% and C max decreased by 32%. Due to modest
decreases in protein binding of aprepitant in patients with renal disease, the
AUC of pharmacologically active unbound drug was not significantly affected in
patients with renal impairment compared with healthy subjects. Hemodialysis
conducted 4 or 48 hours after dosing had no significant effect on the
pharmacokinetics of aprepitant; less than 0.2% of the dose was recovered in the
dialysate.
Hepatic Impairment
Fosaprepitant is metabolized in
various extrahepatic tissues; therefore hepatic impairment is not expected to
alter the conversion of fosaprepitant to aprepitant.
Following administration of a
single 125-mg oral dose of aprepitant on Day 1 and 80 mg once daily on Days 2
and 3 to patients with mild hepatic impairment (Child-Pugh score 5 to 6), the
AUC 0-24hr of aprepitant was 11% lower on Day 1 and 36% lower on Day 3, as
compared with healthy subjects given the same regimen. In patients with
moderate hepatic impairment (Child-Pugh score 7 to 9), the AUC 0-24hr of
aprepitant was 10% higher on Day 1 and 18% higher on Day 3, as compared with
healthy subjects given the same regimen. These differences in AUC 0-24hr are
not considered clinically meaningful. There are no clinical or pharmacokinetic
data in patients with severe hepatic impairment (Child-Pugh score greater than
9) [see Use In Specific Populations].
Body Mass Index (BMI)
For every 5 kg/m² increase
in BMI, AUC 0-24hr and C max of aprepitant decrease by 11%. BMI of subjects in
the analysis ranged from 18 kg/m² to 36 kg/m² . This
change is not considered clinically meaningful.
Drug Interactions Studies
Fosaprepitant, given as a
single 150-mg dose, is a weak inhibitor of CYP3A4, with no evidence of
inhibition or induction of CYP3A4 observed on Day 4. The weak inhibition of
CYP3A4 continues for 2 days after single dose administration of fosaprepitant.
Aprepitant is a substrate, an inhibitor, and an inducer of CYP3A4. Aprepitant
is also an inducer of CYP2C9.
Fosaprepitant or aprepitant is
unlikely to interact with drugs that are substrates for the Pglycoprotein
transporter.
Effects of
Fosaprepitant/Aprepitant on the Pharmacokinetics of Other Drugs
CYP3A4 Substrates
Midazolam: Fosaprepitant 150 mg administered
as a single intravenous dose on Day 1 increased the AUC 0-∞ of midazolam
by approximately 1.8-fold on Day 1 and had no effect on Day 4 when midazolam
was coadministered as a single oral dose of 2 mg on Days 1 and 4.
Corticosteroids
Dexamethasone: Fosaprepitant
administered as a single 150 mg intravenous dose on Day 1 increased the AUC 0-24hr
of dexamethasone, administered as a single 8-mg oral dose on Days 1, 2, and 3,
by approximately 2-fold on Days 1 and 2 [see DOSAGE AND ADMINISTRATION, DRUG
INTERACTIONS].
Methylprednisolone: W hen oral aprepitant as
a 3-day regimen (125-mg/80-mg/80-mg) was administered with intravenous
methylprednisolone 125 mg on Day 1 and oral methylprednisolone 40 mg on Days 2
and 3, the AUC of methylprednisolone was increased by 1.34-fold on Day 1 and by
2.5-fold on Day 3 [see DRUG INTERACTIONS].
Chemotherapeutic Agents
Docetaxel: In a pharmacokinetic
study, oral aprepitant administered as a 3-day regimen (125mg/80-mg/80-mg) did
not influence the pharmacokinetics of docetaxel.
Vinorelbine: In a pharmacokinetic
study, oral aprepitant administered as a 3-day regimen (125mg/80-mg/80-mg) did
not influence the pharmacokinetics of vinorelbine to a clinically significant
degree.
Oral contraceptives: W hen oral aprepitant was
administered as a 3-day regimen (125-mg/80-mg/80mg) with ondansetron and
dexamethasone, and coadministered with an oral contraceptive containing ethinyl
estradiol and norethindrone, the trough concentrations of both ethinyl
estradiol and norethindrone were reduced by as much as 64% for 3 weeks
post-treatment [see DRUG INTERACTIONS].
CYP2C9 Substrates (Warfarin,
Tolbutamide)
Warfarin: A single 125-mg dose of
oral aprepitant was administered on Day 1 and 80 mg/day on Days 2 and 3 to
subjects who were stabilized on chronic warfarin therapy. Although there was no
effect of oral aprepitant on the plasma AUC of R(+) or S(-) warfarin determined
on Day 3, there was a 34% decrease in S(-) warfarin trough concentration
accompanied by a 14% decrease in the prothrombin time (reported as
International Normalized Ratio or INR) 5 days after completion of dosing with
oral aprepitant [see DRUG INTERACTIONS].
Tolbutamide: Oral aprepitant, when
given as 125 mg on Day 1 and 80 mg/day on Days 2 and 3, decreased the AUC of
tolbutamide by 23% on Day 4, 28% on Day 8, and 15% on Day 15, when a single
dose of tolbutamide 500 mg was administered prior to the administration of the
3-day regimen of oral aprepitant and on Days 4, 8, and 15. This effect was not
considered clinically important.
Other Drugs
P-glycoprotein substrates: Aprepitant is unlikely to
interact with drugs that are substrates for the Pglycoprotein transporter, as
demonstrated by the lack of interaction of oral aprepitant with digoxin in a
clinical drug interaction study.
5-HT3 antagonists: In clinical drug
interaction studies, aprepitant did not have clinically important effects on
the pharmacokinetics of ondansetron, granisetron, or hydrodolasetron (the
active metabolite of dolasetron).
Effect of Other Drugs on the
Pharmacokinetics of Fosaprepitant/Aprepitant
Rifampin: W hen a single 375-mg
dose of oral aprepitant was administered on Day 9 of a 14-day regimen of 600
mg/day of rifampin, a strong CYP3A4 inducer, the AUC of aprepitant decreased
approximately 11-fold and the mean terminal half-life decreased approximately
3-fold [see DRUG INTERACTIONS].
Ketoconazole: W hen a single 125-mg
dose of oral aprepitant was administered on Day 5 of a 10-day regimen of 400
mg/day of ketoconazole, a strong CYP3A4 inhibitor, the AUC of aprepitant increased
approximately 5-fold and the mean terminal half-life of aprepitant increased
approximately 3-fold [see DRUG INTERACTIONS].
Diltiazem: In a study in 10 patients
with mild to moderate hypertension, administration of 100 mg of fosaprepitant
as an intravenous infusion with 120 mg of diltiazem, a moderate CYP3A4
inhibitor administered three times daily, resulted in a 1.5-fold increase in
the aprepitant AUC and a 1.4-fold increase in the diltiazem AUC.
When fosaprepitant was
administered with diltiazem, the mean maximum decrease in diastolic blood
pressure was significantly greater than that observed with diltiazem alone
[24.3 ± 10.2 mm Hg with fosaprepitant versus 15.6 ± 4.1 mm Hg without
fosaprepitant]. The mean maximum decrease in systolic blood pressure was also
greater after co-administration of diltiazem with fosaprepitant than administration
of diltiazem alone [29.5 ± 7.9 mm Hg with fosaprepitant versus 23.8 ± 4.8 mm Hg
without fosaprepitant]. Co-administration of fosaprepitant and diltiazem;
however, did not result in any additional clinically significant changes in
heart rate or PR interval, beyond those changes observed with diltiazem alone [see
DRUG INTERACTIONS].
Paroxetine: Coadministration of once
daily doses of oral aprepitant 170 mg, with paroxetine 20 mg once daily,
resulted in a decrease in AUC by approximately 25% and C max by approximately
20% of both aprepitant and paroxetine. This effect was not considered
clinically important.
Clinical Studies
Prevention Of Nausea And Vomiting
Associated With HEC
In a randomized, parallel,
double-blind, active-controlled study, EMEND for injection 150 mg as a single
intravenous infusion (N=1147) was compared to a 3-day oral EMEND regimen
(N=1175) in patients receiving a HEC regimen that included cisplatin ( ≥ 70
mg/m²). All patients in both groups received dexamethasone and
ondansetron (see Table 7). Patient demographics were similar between the two
treatment groups. Of the total 2322 patients, 63% were men, 56% W hite, 26%
Asian, 3% American Indian/Alaska Native, 2% Black, 13% Multi-Racial, and 33%
Hispanic/Latino ethnicity. Patient ages ranged from 19 to 86 years of age, with
a mean age of 56 years. Other concomitant chemotherapy agents commonly
administered were fluorouracil (17%), gemcitabine (16%), paclitaxel (15%), and
etoposide (12%).
Table 7 : Treatment Regimens
in HEC Trial*
|
Day 1 |
Day 2 |
Day 3 |
Day 4 |
EMEND Regimen |
EMEND for injection |
150 mg intravenously over 20 to 30 minutes approximately 30 minutes prior to chemotherapy |
none |
none |
none |
Oral dexamethasone† |
12 mg |
8 mg |
8 mg twice daily |
8 mg twice daily |
Ondansetron |
Ondansetron‡ |
none |
none |
none |
Oral EMEND Regimen |
EMEND capsules |
125 mg |
80 mg |
80 mg |
none |
Oral dexamethasone§ |
12 mg |
8 mg |
8 mg |
8 mg |
Ondansetron |
Ondansetron‡ |
none |
none |
none |
*EMEND for injection placebo,
EMEND capsules placebo and dexamethasone placebo (in the evenings on Days 3 and
4) were used to maintain blinding.
†Dexamethasone was administered 30 minutes prior to chemotherapy
treatment on Day 1 and in the morning on Days 2 through 4. Dexamethasone was
also administered in the evenings on Days 3 and 4. The 12 mg dose of
dexamethasone on Day 1 and the 8 mg once daily dose on Day 2 reflects a dosage
adjustment to account for a drug interaction with the EMEND for injection
regimen [see Pharmacokinetics].
‡Ondansetron 32 mg intravenous was used in the clinical trials of EMEND.
Although this dose was used in clinical trials, this is no longer the currently
recommended dose. Refer to the ondansetron prescribing information for the
current recommended dose.
§Dexamethasone was administered 30 minutes prior to chemotherapy
treatment on Day 1 and in the morning on Days 2 through 4. The 12 mg dose of
dexamethasone on Day 1 and the 8 mg once daily dose on Days 2 through 4
reflects a dosage adjustment to account for a drug interaction with the oral
EMEND regimen [see Pharmacokinetics]. |
The efficacy of EMEND for injection
was evaluated based on the primary and secondary endpoints listed in Table 8
and was shown to be non-inferior to that of the 3-day oral aprepitant regimen
with regard to complete response in each of the evaluated phases. The
pre-specified non-inferiority margin for complete response in the overall phase
was 7%. The pre-specified non-inferiority margin for complete response in the
delayed phase was 7.3%. The pre-specified non-inferiority margin for no
vomiting in the overall phase was 8.2%.
Table 8 : Percent of
Patients Receiving Highly Emetogenic Chemotherapy Responding by Treatment Group
and Phase — Cycle 1
ENDPOINTS |
EMEND for Injection Regimen
(N = 1106)* % |
Oral EMEND Regimen
(N = 1134)* % |
Difference† (95% CI) |
PRIMARY ENDPOINT |
Complete Response‡ |
|
|
|
Overall§ |
71.9 |
72.3 |
-0.4
(-4.1, 3.3) |
SECONDARY ENDPOINTS |
Complete Response‡ |
Delayed phase¶ |
74.3 |
74.2 |
0.1
(-3.5, 3.7) |
No Vomiting |
Overall§ |
72.9 |
74.6 |
-1.7
(-5.3, 2.0) |
*N: Number of patients included
in the primary analysis of complete response.
†Difference and Confidence interval (CI) were calculated using the
method proposed by Miettinen and Nurminen and adjusted for Gender.
‡Complete Response = no vomiting and no use of rescue therapy.
§Overall = 0 to 120 hours post-initiation of cisplatin chemotherapy.
¶ Delayed phase = 25 to 120 hours post-initiation of cisplatin
chemotherapy. |
Prevention Of Nausea And Vomiting
Associated With MEC
In a randomized, parallel,
double-blind, active comparator-controlled study, EMEND for injection 150 mg as
a single intravenous infusion (N=502) in combination with ondansetron and
dexamethasone (EMEND regimen) was compared with ondansetron and dexamethasone
alone (standard therapy) (N=498) (see Table 9) in patients receiving a MEC
regimen. Patient demographics were similar between the two treatment groups. Of
the total 1,000 patients included in the efficacy analysis, 41% were men, 84% W
hite, 4% Asian, 1% American Indian/Alaska Native, 2% Black, 10% Multi-Racial,
and 19% Hispanic/Latino ethnicity. Patient ages ranged from 23 to 88 years of
age, with a mean age of 60 years. The most commonly administered MEC
chemotherapeutic agents were carboplatin (51%), oxaliplatin (24%), and
cyclophosphamide (12%).
Table 9 : Treatment Regimens
in MEC Trial*
|
Day 1 |
Day 2 |
Day 3 |
EMEND Regimen |
EMEND for Injection |
150 mg intravenously over 20 to 30 minutes approximately 30 minutes prior to chemotherapy |
none |
none |
Oral Dexamethasone† |
12 mg |
none |
none |
Oral Ondansetron‡ |
8 mg for 2 doses |
none |
none |
Standard Therapy |
Oral Dexamethasone |
20 mg |
none |
none |
Oral Ondansetron‡ |
8 mg for 2 doses |
8 mg twice daily |
8 mg twice daily |
*EMEND for injection placebo
and dexamethasone placebo (on Day 1) were used to maintain blinding.
†Dexamethasone was administered 30 minutes prior to chemotherapy treatment on
Day 1. The 12 mg dose reflects a dosage adjustment to account for a drug
interaction with the EMEND for injection regimen [see Pharmacokinetics].
‡The first ondansetron dose was administered 30 to 60 minutes prior to
chemotherapy treatment on Day 1 and the second dose was administered 8 hours
after first ondansetron dose. |
The primary endpoint was
complete response (defined as no vomiting and no rescue therapy) in the delayed
phase (25 to 120 hours) of chemotherapy-induced nausea and vomiting. The
results by treatment group are shown in Table 10.
Table 10 : Percent of
Patients Receiving Moderately Emetogenic Chemotherapy Responding by Treatment
Group
ENDPOINTS |
EMEND for Injection Regimen
(N = 502)* % |
Standard Therapy Regimen
(N = 498)* % |
P-Value |
T reatment Difference (95% CI) |
PRIMARY ENDPOIN |
Complete Response† |
Delayed phase‡ |
78.9 |
68.5 |
< 0.001 |
10.4
(5.1, 15.9) |
*N: Number of patients included
in the intention to treat population.
†Complete Response = no vomiting and no use of rescue therapy.
‡Delayed phase = 25 to 120 hours post-initiation of chemotherapy. |