Aprepitant (Page 5 of 10)

11 DESCRIPTION

Aprepitant Capsules USP contain the active ingredient aprepitant, USP. Aprepitant, USP is a substance P/neurokinin 1 (NK1 ) receptor antagonist, an antiemetic agent, chemically described as 5-[[(2R ,3S)-2-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-3-(4-fluorophenyl)-4-morpholinyl]methyl]-1,2-dihydro-3H -1,2,4-triazol-3-one.

Its empirical formula is C23 H21 F7 N4 O3 , and its structural formula is:

Structure
(click image for full-size original)

Aprepitant, USP is a white to off-white powder, with a molecular weight of 534.43 g/mol. It is soluble in methanol and in acetone, sparingly soluble in ethanol, and practically insoluble in water.

Each capsule for oral administration contains either 40 mg, 80 mg, or 125 mg of aprepitant, USP and the following inactive ingredients: colloidal silicon dioxide, hydroxyethyl cellulose, microcrystalline cellulose, mannitol, poloxamer, povidone, sodium stearyl fumarate, vitamin E polyethylene glycol succinate, and purified water. The capsule shell excipients are gelatin, sodium lauryl sulphate and titanium dioxide. The 40-mg capsule shell also contains iron oxide yellow, and the 125 mg capsule also contains FD&C Red #3. Non-volatile solvents in the imprinting ink are shellac, iron oxide black and potassium hydroxide.

USP dissolution test pending.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

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) and postoperative nausea and vomiting (PONV).

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.

12.2 Pharmacodynamics

NK1 Receptor Occupancy

In two single-blind, multiple-dose, randomized, and placebo-controlled studies, healthy young men received oral aprepitant doses of 10 mg (N=2), 30 mg (N=3), 100 mg (N=3) or 300 mg (N=5) once daily (0.08, 0.24, 0.8, and 2.4 times the maximum recommended single dose, respectively) for 14 days with 2 or 3 subjects on placebo. Both plasma aprepitant concentration and NK1 receptor occupancy in the corpus striatum by positron emission tomography were evaluated, at predose and 24 hours after the last dose. At aprepitant plasma concentrations of approximately 10 ng/mL and 100 ng/mL, the NK1 receptor occupancies were approximately 50% and 90%, respectively. The oral aprepitant regimen produced mean trough plasma aprepitant concentrations greater than 500 ng/mL in adults, which would be expected to, based on the fitted curve with the Hill equation, result in greater than 95% brain NK1 receptor occupancy. However, the receptor occupancy has not been determined. In addition, the relationship between NK1 receptor occupancy and the clinical efficacy of aprepitant has not been established.

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. Maximum aprepitant concentrations after a single 200-mg dose of fosaprepitant were 4- and 9-fold higher than that achieved with oral aprepitant 125 mg and 40 mg, respectively. QT prolongation with the oral aprepitant dosing regimens is not expected.

12.3 Pharmacokinetics

Absorption

Following oral administration of a single 40 mg dose of aprepitant in the fasted state, mean area under the plasma concentration-time curve (AUC0-∞ ) was 7.8 mcg•hr/mL and mean peak plasma concentration (Cmax ) was 0.7 mcg/mL, occurring at approximately 3 hours postdose (Tmax ). The absolute bioavailability at the 40 mg dose has not been determined.

Following oral administration of a single 125 mg dose of aprepitant on Day 1 and 80 mg once daily on Days 2 and 3, the AUC0-24hr was approximately 19.6 mcg•hr/mL and 21.2 mcg•hr/mL on Day 1 and Day 3, respectively. The Cmax of 1.6 mcg/mL and 1.4 mcg/mL were reached in approximately 4 hours (Tmax ) on Day 1 and Day 3, respectively. At the dose range of 80 to 125 mg, the mean absolute oral bioavailability of aprepitant is approximately 60 to 65%. Oral administration of the capsule with a standard high-fat breakfast had no clinically meaningful effect on the bioavailability of aprepitant.

The pharmacokinetics of aprepitant were non-linear across the clinical dose range. In healthy young adults, the increase in AUC0-∞ was 26% greater than dose proportional between 80 mg and 125 mg single doses administered in the fed state.

Distribution

Aprepitant is greater than 95% bound to plasma proteins. The mean apparent volume of distribution at steady state (Vdss ) was approximately 70 L in humans.

Aprepitant crosses the blood brain barrier in humans [see Clinical Pharmacology (12.1)].

Elimination

Metabolism

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 [14 C]-aprepitant (2.4 times the maximum recommended dose), 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 [14 C]-aprepitant prodrug to healthy subjects, 57% of the radioactivity was recovered in urine and 45% in feces. A study was not conducted with radiolabeled capsule formulation. The results after oral administration may differ.

Aprepitant is eliminated primarily by metabolism; aprepitant is not renally excreted. The apparent plasma clearance of aprepitant ranged from approximately 62 to 90 mL/min. The apparent terminal half-life ranged from approximately 9 to 13 hours.

Specific Populations

Geriatric Patients

Following oral administration of a single 125 mg dose of aprepitant on Day 1 and 80 mg once daily on Days 2 through 5 (2 additional days of dosing compared to the recommended duration), the AUC0-24hr 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 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 [see Use in Specific Populations ( Error! Hyperlink reference not valid. )].

Pediatric Patients

As part of a 3-day regimen, dosing of aprepitant capsules (125 mg/80 mg/80 mg) in 18 pediatric patients (aged 12 through 17 years) achieved a mean AUC0-24hr of 17 mcg•hr/mL on Day 1 with mean peak plasma concentration (Cmax ) at 1.3 mcg/mL occurring at approximately 4 hours. The mean concentrations at the end of Day 2 (N=8) and Day 3 (N=16) were both at 0.6 mcg/mL.

A population pharmacokinetic analysis of aprepitant in pediatric patients (aged 6 months through 17 years) suggests that sex and race have no clinically meaningful effect on the pharmacokinetics of aprepitant.

Male and Female Patients

Following oral administration of a single dose of aprepitant ranging from 40 mg to 375 mg (3 times the maximum aprepitant recommended dose), the AUC0-24hr and Cmax are 9% and 17% higher in females as compared with males. The half-life of aprepitant is approximately 25% lower in females as compared with males and Tmax occurs at approximately the same time. These differences are not considered clinically meaningful.

Racial or Ethnic Groups

Following oral administration of a single dose of aprepitant ranging from 40 mg to 375 mg (3 times the maximum aprepitant recommended dose), the AUC0-24hr and Cmax are approximately 27% and 19% higher in Hispanics as compared with Caucasians. The AUC0-24hr and Cmax were 74% and 47% higher in Asians as compared to Caucasians. There was no difference in AUC0-24hr or Cmax between Caucasians and Blacks. These differences are not considered clinically meaningful.

Patients with Renal Impairment

A single 240 mg dose of aprepitant (approximately 1.9 times the maximum aprepitant recommended dose) 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 AUC0-∞ of total aprepitant (unbound and protein bound) decreased by 21% and Cmax 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 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 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 [see Use in Specific Populations (8.6)].

Patients with Hepatic Impairment

Following administration of a single 125 mg 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 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 impairment (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. There are no clinical or pharmacokinetic data in patients with severe hepatic impairment (Child-Pugh score greater than 9) [see Use in Specific Populations (8.7)].

Body Mass Index (BMI)

For every 5 kg/m2 increase in BMI, AUC0-24hr and Cmax of aprepitant decrease by 9% and 10%. 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

Aprepitant is a substrate, a moderate (dose-dependent) inhibitor, and an inducer of CYP3A4. Aprepitant is also an inducer of CYP2C9. Aprepitant is unlikely to interact with drugs that are substrates for the P-glycoprotein transporter.

Effects of Aprepitant on the Pharmacokinetics of Other Drugs

CYP3A4 substrates (i.e., midazolam): Interactions between aprepitant and coadministered midazolam are listed in Table 12 (increase is indicated as “↑”, decrease as “↓”, no change as “↔”).

Table 9: Pharmacokinetic Interaction Data for Aprepitant and Coadministered Midazolam
Dosage of Aprepitant Dosage of Midazolam Observed Drug Interactions

Aprepitant 125 mg on Day 1 and 80 mg on Days 2 to 5

oral 2 mg single dose on Days 1 and 5

midazolam AUC ↑ 2.3-fold on Day 1 and ↑ 3.3-fold on Day 5 [see Drug Interactions (7.1)]

Aprepitant 125 mg on Day 1 and 80 mg on Days 2 and 3

intravenous 2 mg prior to 3-day regimen of aprepitant and on Days 4, 8 and 15

midazolam AUC ↑ 25% on Day 4, AUC ↓ 19% on Day 8 and AUC ↓ 4% on Day 15

Aprepitant 125 mg

intravenous 2 mg given 1 hour after aprepitant

midazolam AUC ↑ 1.5-fold

Aprepitant 40 mg

oral 2 mg

midazolam AUC ↑ 1.2-fold on Day 1

A difference of less than 2-fold increase of midazolam AUC is not considered clinically important.

Corticosteroids:

Dexamethasone: Aprepitant, when given as a regimen of 125 mg on Day 1 and 80 mg/day on Days 2 through 5, coadministered with 20 mg dexamethasone on Day 1 and 8 mg dexamethasone on Days 2 through 5, increased the AUC of dexamethasone by 2.2-fold on Days 1 and 5 [see Dosage and Administration (2.1)]. A single dose of aprepitant (40 mg) when coadministered with a single dose of dexamethasone 20 mg, increased the AUC of dexamethasone by 1.45-fold, which is not considered clinically significant.

Methylprednisolone: Aprepitant, when given as a regimen of 125 mg on Day 1 and 80 mg/day on Days 2 and 3, coadministered with 125 mg methylprednisolone IV on Day 1 and 40 mg methylprednisolone orally on Days 2 and 3, increased the AUC of methylprednisolone by 1.34-fold on Day 1 and by 2.5-fold on Day 3.

Chemotherapeutic agents:

Docetaxel: In a pharmacokinetic study, aprepitant (125 mg/80 mg/80 mg regimen) did not influence the pharmacokinetics of docetaxel.

Vinorelbine: In a pharmacokinetic study, aprepitant (125 mg/80 mg/80 mg regimen) did not influence the pharmacokinetics of vinorelbine to a clinically significant degree.

CYP2C9 substrates (Warfarin, Tolbutamide):

Warfarin: A single 125 mg dose of aprepitant was administered on Day 1 and 80 mg/day on Days 2 and 3 to healthy subjects who were stabilized on chronic warfarin therapy. Although there was no effect of 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 aprepitant [see Drug Interactions (7.1)].

Tolbutamide: 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 aprepitant and on Days 4, 8, and 15. This effect was not considered clinically important.

Aprepitant, when given as a 40 mg single dose on Day 1, decreased the AUC of tolbutamide by 8% on Day 2, 16% on Day 4, 15% on Day 8, and 10% on Day 15, when a single dose of tolbutamide 500 mg was administered prior to the administration of aprepitant 40 mg and on Days 2, 4, 8, and 15. This effect was not considered significant.

Other Drugs

Oral contraceptives: When aprepitant was administered as a 3-day regimen (125 mg/80 mg/80 mg) 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.

P-glycoprotein substrates: Aprepitant is unlikely to interact with drugs that are substrates for the P-glycoprotein transporter, as demonstrated by the lack of interaction of 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 Aprepitant

Ketoconazole: When a single 125 mg dose of 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 (7.2)].

Rifampin: When a single 375 mg dose of aprepitant (3 times the maximum aprepitant recommended dose) 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 (7.2)].

Diltiazem: In patients with mild to moderate hypertension, administration of aprepitant once daily, as a tablet formulation comparable to 230 mg of the capsule formulation (approximately 1.8 times the aprepitant recommended dose), with diltiazem 120 mg 3 times daily for 5 days, resulted in a 2-fold increase of aprepitant AUC and a simultaneous 1.7-fold increase of diltiazem AUC. These pharmacokinetic effects did not result in clinically meaningful changes in ECG, heart rate or blood pressure beyond those changes induced by diltiazem alone [see Drug Interactions (7.2)].

Paroxetine: Coadministration of once daily doses of aprepitant, as a tablet formulation comparable to 85 mg or 170 mg of the capsule formulation (approximately 0.7 and 1.4 times the aprepitant maximum recommended dose), with paroxetine 20 mg once daily, resulted in a decrease in AUC by approximately 25% and Cmax by approximately 20% of both aprepitant and paroxetine. This effect was not considered clinically important.

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