Fosaprepitant, a prodrug of aprepitant, when administered intravenously is
rapidly converted to aprepitant, a substance P/neurokinin 1 (NK1) receptor antagonist.
Plasma concentrations of fosaprepitant are below the limits of quantification
(10 ng/mL) within 30 minutes of the completion of infusion (see CLINICAL
PHARMACOLOGY, Pharmacokinetics). Upon conversion of 115 mg of fosaprepitant
to aprepitant, 18.3 mg of phosphate and 73 mg of meglumine are liberated from
fosaprepitant.
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-HT3), 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 NK1 receptors. Animal and human
studies show that aprepitant augments the antiemetic activity of the 5-HT3-receptor
antagonist ondansetron and the corticosteroid dexamethasone and inhibits both
the acute and delayed phases of cisplatin-induced emesis.
Pharmacokinetics
Aprepitant after Fosaprepitant Administration
Following a single intravenous dose of fosaprepitant administered as a 15-minute
infusion to healthy volunteers the mean AUC0-∞ of aprepitant was 31.7
(± 14.3) mcg• hr/mL and the mean maximal aprepitant concentration
(Cmax) was 3.27 (± 1.16) mcg/mL. The mean aprepitant plasma concentration
at 24 hours postdose was similar between the 125-mg oral aprepitant dose and
the 115-mg intravenous fosaprepitant dose (See Figure 1).
Figure 1: Mean Plasma Concentration of Aprepitant Following
125-mg Oral Aprepitant and 115-mg I.V. Fosaprepitant
Distribution
Fosaprepitant is rapidly converted to aprepitant. Aprepitant is greater than
95% bound to plasma proteins. The mean apparent volume of distribution at steady
state (Vdss) is approximately 70 L in humans.
Aprepitant crosses the placenta in rats and rabbits and crosses the blood brain
barrier in humans (see CLINICAL PHARMACOLOGY, Mechanism of Action).
Metabolism
Fosaprepitant was rapidly converted to aprepitant in in vitro incubations
with liver preparations from nonclinical species (rat and dog) and humans. Furthermore,
fosaprepitant underwent rapid and nearly complete conversion to aprepitant 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. In humans,
fosaprepitant administered intravenously was rapidly converted to aprepitant
within 30 minutes following the end of infusion.
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 I.V. 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 of aprepitant ranged from approximately
9 to 13 hours.
Special Populations
Fosaprepitant, a prodrug of aprepitant, when administered intravenously is
rapidly converted to aprepitant.
Gender
Following oral administration of a single 125-mg dose of aprepitant, no difference
in AUC0-24hr was observed between males and females. The Cmax for
aprepitant is 16% higher in females as compared with males. The half-life of
aprepitant is 25% lower in females as compared with males and Tmax occurs at
approximately the same time. These differences are not considered clinically
meaningful. No dosage adjustment is necessary based on gender.
Geriatric
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 AUC0-24hr of aprepitant
was 21% higher on Day 1 and 36% higher on Day 5 in elderly ( ≥ 65 years) relative
to younger adults. The Cmax 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. No dosage adjustment is necessary in elderly patients.
Pediatric
Fosaprepitant has not been evaluated in patients below 18 years of age.
Race
Following oral administration of a single 125-mg dose of aprepitant, the AUC0-24hr
is approximately 25% and 29% higher in Hispanics as compared with Whites
and Blacks, respectively. The C max is 22% and 31% higher in Hispanics as compared
with Whites and Blacks, respectively. These differences are not considered clinically
meaningful. There was no difference in AUC0-24hr or Cmax between
Whites and Blacks. No dosage adjustment is necessary based on race.
Hepatic Insufficiency
Fosaprepitant is metabolized in various extrahepatic tissues; therefore hepatic
insufficiency is not expected to alter the conversion of fosaprepitant to aprepitant.
Oral aprepitant was well tolerated in patients with mild to moderate hepatic
insufficiency. Following administration of a single 125-mg dose of oral aprepitant
on Day 1 and 80 mg once daily on Days 2 and 3 to patients with mild hepatic
insufficiency (Child-Pugh score 5 to 6), the AUC0-24hr 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 insufficiency (Child-Pugh
score 7 to 9), the AUC0-24hr 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 AUC0-24hr are not considered clinically
meaningful; therefore, no dosage adjustment is necessary in patients with mild
to moderate hepatic insufficiency. There are no clinical or pharmacokinetic
data in patients with severe hepatic insufficiency (Child-Pugh score > 9)
(see PRECAUTIONS).
Renal Insufficiency
A single 240-mg dose of oral aprepitant was administered to patients with severe
renal insufficiency (CrCl < 30 mL/min) and to patients with end stage renal
disease (ESRD) requiring hemodialysis.
In patients with severe renal insufficiency, the AUC0-∞ of
total aprepitant (unbound and protein bound) decreased by 21% and Cmax decreased
by 32%, relative to healthy subjects. In patients with ESRD undergoing hemodialysis,
the AUC0-∞ of total aprepitant decreased by 42% and Cmax 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 insufficiency 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.
No dosage adjustment is necessary for patients with renal insufficiency or
for patients with ESRD undergoing hemodialysis.
Pharmacodynamics
Cardiac Electrophysiology
In a randomized, double-blind, positive-controlled, thorough QTc study, a single
200-mg dose of fosaprepitant had no effect on the QTc interval.
Clinical Studies
Fosaprepitant, a prodrug of aprepitant, when administered intravenously is
rapidly converted to aprepitant. Fosaprepitant 115 mg I.V. infused over 15 minutes
can be substituted for 125 mg oral aprepitant on Day 1 (see DOSAGE AND ADMINISTRATION).
Pivotal efficacy studies were conducted with oral aprepitant.
Oral administration of aprepitant in combination with ondansetron and dexamethasone
(aprepitant regimen) has been shown to prevent acute and delayed nausea and
vomiting associated with highly emetogenic chemotherapy including high-dose
cisplatin, and nausea and vomiting associated with moderately emetogenic chemotherapy.
Highly Emetogenic Chemotherapy
In 2 multicenter, randomized, parallel, double-blind, controlled clinical studies,
the aprepitant regimen (see table below) was compared with standard therapy
in patients receiving a chemotherapy regimen that included cisplatin > 50
mg/m² (mean cisplatin dose = 80.2 mg/m²). Of the 550 patients who
were randomized to receive the aprepitant regimen, 42% were women, 58% men,
59% White, 3% Asian, 5% Black, 12% Hispanic American, and 21% Multi-Racial.
The aprepitant-treated patients in these clinical studies ranged from 14 to
84 years of age, with a mean age of 56 years. 170 patients were 65 years or
older, with 29 patients being 75 years or older.
Patients (N = 1105) were randomized to either the aprepitant regimen (N = 550)
or standard therapy (N = 555). The treatment regimens are defined in the table
below.
Treatment Regimens Highly Emetogenic Chemotherapy Trials
| Treatment Regimen |
Day 1 |
Days 2 to 4 |
| Aprepitant |
Aprepitant 125 mg PO
Dexamethasone 12 mg PO
Ondansetron 32 mg I.V . |
Aprepitant 80 mg PO Daily (Days 2 and 3 only)
Dexamethasone 8 mg PO Daily (morning) |
| Standard Therapy |
Dexamethasone 20 mg PO
Ondansetron 32 mg I.V . |
Dexamethasone 8 mg PO Daily (morning)
Dexamethasone 8 mg PO Daily (evening) |
| Aprepitant placebo and dexamethasone placebo
were used to maintain blinding. |
During these studies 95% of the patients in the aprepitant group received a
concomitant chemotherapeutic agent in addition to protocol-mandated cisplatin.
The most common chemotherapeutic agents and the number of aprepitant patients
exposed follow: etoposide (106), fluorouracil (100), gemcitabine (89), vinorelbine
(82), paclitaxel (52), cyclophosphamide (50), doxorubicin (38), docetaxel (11).
The antiemetic activity of oral aprepitant was evaluated during the acute phase
(0 to 24 hours postcisplatin treatment), the delayed phase (25 to 120 hours
post-cisplatin treatment) and overall (0 to 120 hours post-cisplatin treatment)
in Cycle 1. Efficacy was based on evaluation of the following endpoints:
Primary endpoint:
- complete response (defined as no emetic episodes and no use of rescue therapy)
Other prespecified endpoints:
- complete protection (defined as no emetic episodes, no use of rescue therapy,
and a maximum nausea visual analogue scale [VAS] score < 25 mm on a 0 to
100 mm scale)
- no emesis (defined as no emetic episodes regardless of use of rescue therapy)
- no nausea (maximum VAS < 5 mm on a 0 to 100 mm scale)
- no significant nausea (maximum VAS < 25 mm on a 0 to 100 mm scale)
A summary of the key study results from each individual study analysis is shown
in Table 1 and in Table 2.
Table 1 : Percent of Patients Receiving Highly Emetogenic
Chemotherapy Responding by Treatment Group and Phase for Study 1 — Cycle 1
| ENDPOINTS |
Aprepitant
Regimen
(N = 260)†
% |
Standard
Therapy
(N = 261)†
% |
p-Value |
| PRIMARY ENDPOINT |
| Complete Response |
| Overall‡ |
73 |
52 |
<0.001 |
| OTHER PRESPECIFIED ENDPOINTS |
| Complete Response |
| Acute phase§ |
89 |
78 |
< 0.001 |
| Delayed phase|| |
75 |
56 |
< 0.001 |
| Complete Protection |
| Overall |
63 |
49 |
0.001 |
| Acute phase |
85 |
75 |
NS* |
| Delayed phase |
66 |
52 |
< 0.001 |
| No Emesis |
| Overall |
78 |
55 |
< 0.001 |
| Acute phase |
90 |
79 |
0.001 |
| Delayed phase |
81 |
59 |
< 0.001 |
| No Nausea |
| Overall |
48 |
44 |
NS** |
| Delayed phase |
51 |
48 |
NS** |
| No Significant Nausea |
| Overall |
73 |
66 |
NS** |
| Delayed phase |
75 |
69 |
NS** |
†N: Number of patients
(older than 18 years of age) who received cisplatin, study drug, and had
at least one post-treatment efficacy evaluation.
‡Overall: 0 to 120 hours post-cisplatin treatment.
§Acute phase: 0 to 24 hours post-cisplatin treatment.
||Delayed phase: 25 to 120 hours post-cisplatin treatment.
*Not statistically significant when adjusted for multiple comparisons.
**Not statistically significant.
Visual analogue scale (VAS) score range: 0 mm = no nausea; 100 mm = nausea
as bad as it could be. |
Table 2 : Percent of Patients Receiving Highly Emetogenic
Chemotherapy Responding by Treatment Group and Phase for Study 2 — Cycle 1
| ENDPOINTS |
Aprepitant
Regimen
(N = 261)†
% |
Standard
Therapy
(N = 263) †
% |
p-Value |
| PRIMARY ENDPOINT |
| Complete Response |
| Overall‡ |
63 |
43 |
< 0.001 |
| OTHER PRESPECIFIED ENDPOINTS |
| Complete Response |
| Acute phase§ |
83 |
68 |
< 0.001 |
| Delayed phase|| |
68 |
47 |
< 0.001 |
| Complete Protection |
| Overall |
56 |
41 |
< 0.001 |
| Acute phase |
80 |
65 |
< 0.001 |
| Delayed phase |
61 |
44 |
< 0.001 |
| No Emesis |
| Overall |
66 |
44 |
< 0.001 |
| Acute phase |
84 |
69 |
< 0.001 |
| Delayed phase |
72 |
48 |
< 0.001 |
| No Nausea |
| Overall |
49 |
39 |
NS* |
| Delayed phase |
53 |
40 |
NS* |
| No Significant Nausea |
| Overall |
71 |
64 |
NS** |
| Delayed phase |
73 |
65 |
NS** |
†N: Number of patients
(older than 18 years of age) who received cisplatin, study drug, and had
at least one post-treatment efficacy evaluation.
‡Overall: 0 to 120 hours post-cisplatin treatment.
§Acute phase: 0 to 24 hours post-cisplatin treatment.
||Delayed phase: 25 to 120 hours post-cisplatin treatment.
*Not statistically significant when adjusted for multiple comparisons.
**Not statistically significant.
Visual analogue scale (VAS) score range: 0 mm = no nausea; 100 mm = nausea
as bad as it could be. |
In both studies, a statistically significantly higher proportion of patients
receiving the aprepitant regimen in Cycle 1 had a complete response (primary
endpoint), compared with patients receiving standard therapy. A statistically
significant difference in complete response in favor of the aprepitant regimen
was also observed when the acute phase and the delayed phase were analyzed separately.
In both studies, the estimated time to first emesis after initiation of cisplatin
treatment was longer with the aprepitant regimen, and the incidence of first
emesis was reduced in the aprepitant regimen group compared with standard therapy
group as depicted in the Kaplan-Meier curves in Figure 2.
Figure 2: Percent of Patients Receiving Highly Emetogenic
Chemotherapy Who Remain Emesis Free Over Time – Cycle 1
Patient-Reported Outcomes
The impact of nausea and vomiting on patients' daily lives was assessed in
Cycle 1 of both Phase III studies using the Functional Living Index–Emesis (FLIE),
a validated nauseaand vomiting-specific patient-reported outcome measure. Minimal
or no impact of nausea and vomiting on patients' daily lives is defined as a
FLIE total score > 108. In each of the 2 studies, a higher proportion of patients
receiving the aprepitant regimen reported minimal or no impact of nausea and
vomiting on daily life (Study 1: 74% versus 64%; Study 2: 75% versus 64%).
Multiple-Cycle Extension
In the same 2 clinical studies, patients continued into the Multiple-Cycle
extension for up to 5 additional cycles of chemotherapy. The proportion of patients
with no emesis and no significant nausea by treatment group at each cycle is
depicted in Figure 3. Antiemetic effectiveness for the patients receiving the
aprepitant regimen is maintained throughout repeat cycles for those patients
continuing in each of the multiple cycles.
Figure 3: Proportion of Patients Receiving Highly Emetogenic
Chemotherapy With No Emesis and No Significant Nausea by Treatment Group and
Cycle
Moderately Emetogenic Chemotherapy
In a multicenter, randomized, double-blind, parallel-group, clinical study
in breast cancer patients, the aprepitant regimen (see table that follows) was
compared with a standard of care therapy in patients receiving a moderately
emetogenic chemotherapy regimen that included cyclophosphamide 750-1500 mg/m²;
or cyclophosphamide 500-1500 mg/m² and doxorubicin ( ≤ 60 mg/m²)
or epirubicin ( ≤ 100 mg/m²).
In this study, the most common combinations were cyclophosphamide + doxorubicin
(60.6%); and cyclophosphamide + epirubicin + fluorouracil (21.6%).
Of the 438 patients who were randomized to receive the aprepitant regimen,
99.5% were women. Of these, approximately 80% were White, 8% Black, 8% Asian,
4% Hispanic, and < 1% Other. The aprepitant-treated patients in this clinical
study ranged from 25 to 78 years of age, with a mean age of 53 years; 70 patients
were 65 years or older, with 12 patients being over 74 years.
Patients (N = 866) were randomized to either the aprepitant regimen (N = 438)
or standard therapy (N = 428). The treatment regimens are defined in the table
that follows.
Treatment Regimens Moderately Emetogenic Chemotherapy Trial
| Treatment Regimen |
Day 1 |
Days 2 to 3 |
| Aprepitant |
Aprepitant 125 mg PO†
Dexamethasone 12 mg PO‡
Ondansetron 8 mg PO x 2 doses§ |
Aprepitant 80 mg PO Daily |
| Standard Therapy |
Dexamethasone 20 mg PO
Ondansetron 8 mg PO x 2 doses |
Ondansetron 8 mg PO Daily (every 12 hours) |
Aprepitant placebo and dexamethasone placebo
were used to maintain blinding.
†1 hour prior to chemotherapy.
‡30 minutes prior to chemotherapy.
§30 to 60 minutes prior to chemotherapy and 8 hours after
first ondansetron dose. |
The antiemetic activity of oral aprepitant was evaluated based on the following
endpoints: Primary endpoint:
Complete response (defined as no emetic episodes and no use of rescue therapy)
in the overall phase (0 to 120 hours post-chemotherapy)
Other prespecified endpoints:
- no emesis (defined as no emetic episodes regardless of use of rescue therapy)
- no nausea (maximum VAS < 5 mm on a 0 to 100 mm scale)
- no significant nausea (maximum VAS < 25 mm on a 0 to 100 mm scale)
- complete protection (defined as no emetic episodes, no use of rescue therapy,
and a maximum nausea visual analogue scale [VAS] score < 25 mm on a 0 to
100 mm scale)
- complete response during the acute and delayed phases. A summary of the
key results from this study is shown in Table 3.
Table 3 : Percent of Patients Receiving Moderately Emetogenic
Chemotherapy Responding by Treatment Group and Phase — Cycle 1
| ENDPOINTS |
Aprepitant
Regimen
(N = 433)†
% |
Standard
Therapy
(N = 424)&dagger
;% |
p-Value |
| PRIMARY ENDPOINT |
| Complete Response‡ |
51 |
42 |
0.015 |
| OTHER PRESPECIFIED ENDPOINTS |
| No Emesis |
76 |
59 |
NS* |
| No Nausea |
33 |
33 |
NS |
| No Significant Nausea |
61 |
56 |
NS |
| No Rescue Therapy |
59 |
56 |
NS |
| Complete Protection |
43 |
37 |
NS |
†N: Number of patients
included in the primary analysis of complete response.
‡Overall: 0 to 120 hours post-chemotherapy treatment.
*NS when adjusted for prespecified multiple comparisons rule; unadjusted
p-value < 0.001. |
In this study, a statistically significantly (p=0.015) higher proportion of
patients receiving the aprepitant regimen (51%) in Cycle 1 had a complete response
(primary endpoint) during the overall phase compared with patients receiving
standard therapy (42%). The difference between treatment groups was primarily
driven by the “No Emesis Endpoint”, a principal component of this
composite primary endpoint. In addition, a higher proportion of patients receiving
the aprepitant regimen in Cycle 1 had a complete response during the acute (0-24
hours) and delayed (25-120 hours) phases compared with patients receiving standard
therapy; however, the treatment group differences failed to reach statistical
significance, after multiplicity adjustments.
Patient-Reported Outcomes
In a phase III study in patients receiving moderately emetogenic chemotherapy,
the impact of nausea and vomiting on patients' the FLIE. A higher proportion
of patients receiving the aprepitant regimen reported minimal or no impact on
daily life (64% versus 56%). This difference between treatment groups was primarily
driven by the “No Vomiting Domain” of this composite endpoint.
Multiple-Cycle Extension
Patients receiving moderately emetogenic chemotherapy were permitted to continue
into the Multiple-Cycle extension of the study for up to 3 additional cycles
of chemotherapy. Antiemetic effect for patients receiving the aprepitant regimen
is maintained during all cycles.
Last updated on RxList: 3/11/2009