Austedo: Package Insert and Label Information (Page 3 of 5)

10 OVERDOSAGE

Overdoses ranging from 100 mg to 1 g have been reported in the literature with tetrabenazine, a closely related VMAT2 inhibitor. The following adverse reactions occurred with overdosing: acute dystonia, oculogyric crisis, nausea and vomiting, sweating, sedation, hypotension, confusion, diarrhea, hallucinations, rubor, and tremor.

Treatment should consist of those general measures employed in the management of overdosage with any central nervous system-active drug. General supportive and symptomatic measures are recommended. Cardiac rhythm and vital signs should be monitored. In managing overdosage, the possibility of multiple drug involvement should always be considered. The physician should consider contacting a poison control center on the treatment of any overdose. Telephone numbers for certified poison control centers are listed on the American Association of Poison Control Centers website www.aapcc.org.

11 DESCRIPTION

AUSTEDO (deutetrabenazine) is a vesicular monoamine transporter 2 (VMAT2) inhibitor for oral administration. The molecular weight of deutetrabenazine is 323.46; the pKa is 6.31. Deutetrabenazine is a hexahydro-dimethoxybenzoquinolizine derivative and has the following chemical name: (RR, SS)-1, 3, 4, 6, 7, 11b-hexahydro-9, 10-di(methoxy-d3 )-3-(2-methylpropyl)-2H-benzo[a]quinolizin-2-one.

The molecular formula for deutetrabenazine is C19 H21 D6 NO3 . Deutetrabenazine is a racemic mixture containing the following structures:

chemical-structure.jpg
(click image for full-size original)

Deutetrabenazine is a white to slightly yellow crystalline powder that is sparingly soluble in water and soluble in ethanol.

AUSTEDO tablets contain 6 mg, 9 mg, or 12 mg deutetrabenazine, and the following inactive ingredients: ammonium hydroxide, black iron oxide, n-butyl alcohol, butylated hydroxyanisole, butylated hydroxytoluene, magnesium stearate, mannitol, microcrystalline cellulose, polyethylene glycol, polyethylene oxide, polysorbate 80, polyvinyl alcohol, povidone, propylene glycol, shellac, talc, titanium dioxide, and FD&C blue #2 lake. The 6 mg tablets also contain FD&C red #40 lake. The 12 mg tablets also contain FD&C yellow #6 lake.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

The precise mechanism by which deutetrabenazine exerts its effects in the treatment of tardive dyskinesia and chorea in patients with Huntington’s disease is unknown but is believed to be related to its effect as a reversible depletor of monoamines (such as dopamine, serotonin, norepinephrine, and histamine) from nerve terminals. The major circulating metabolites (α-dihydrotetrabenazine [HTBZ] and β-HTBZ) of deutetrabenazine, are reversible inhibitors of VMAT2, resulting in decreased uptake of monoamines into synaptic vesicles and depletion of monoamine stores.

12.2 Pharmacodynamics

Cardiac Electrophysiology

At the maximum recommended dose, AUSTEDO does not prolong the QT interval to any clinically relevant extent. An exposure-response analysis on QTc prolongation from a study in extensive or intermediate (EM) and poor CYP2D6 metabolizers (PM) showed that a clinically-relevant effect can be excluded at exposures following single doses of 24 and 48 mg of AUSTEDO.

Melanin Binding

Deutetrabenazine or its metabolites bind to melanin-containing tissues (i.e., eye, skin, fur) in pigmented rats. After a single oral dose of radiolabeled deutetrabenazine, radioactivity was still detected in eye and fur at 35 days following dosing [see Warnings and Precautions (5.9)].

12.3 Pharmacokinetics

After oral dosing up to 25 mg, plasma concentrations of deutetrabenazine are generally below the limit of detection because of the extensive hepatic metabolism of deutetrabenazine to the active deuterated dihydro metabolites (HTBZ), α-HTBZ and β-HTBZ. Linear dose dependence of Cmax and AUC was observed for the active metabolites following single or multiple doses of deutetrabenazine (6 mg to 24 mg and 7.5 mg twice daily to 22.5 mg twice daily).

Absorption

Following oral administration of deutetrabenazine, the extent of absorption is at least 80%.

Plasma concentrations of deutetrabenazine are generally below the limit of detection after oral dosing. Peak plasma concentrations (Cmax ) of deuterated α-HTBZ and β-HTBZ are reached within 3 to 4 hours after dosing.

Effect of Food

The effects of food on the bioavailability of AUSTEDO were studied in subjects administered a single dose with and without food. Food had no effect on the area under the plasma concentration-time curve (AUC) of α-HTBZ or β-HTBZ, although Cmax was increased by approximately 50% in the presence of food [see Dosage and Administration (2.1)].

Distribution

The median volume of distribution (Vc/F) of the α-HTBZ, and the β-HTBZ metabolites of AUSTEDO are approximately 500 L and 730 L, respectively.

Results of PET-scan studies in humans show that following intravenous injection of 11 C-labeled tetrabenazine or α-HTBZ, radioactivity is rapidly distributed to the brain, with the highest binding in the striatum and lowest binding in the cortex.

The in vitro protein binding of tetrabenazine, α-HTBZ, and β-HTBZ was examined in human plasma for concentrations ranging from 50 to 200 ng/mL. Tetrabenazine binding ranged from 82% to 85%, α-HTBZ binding ranged from 60% to 68%, and β-HTBZ binding ranged from 59% to 63%.

Elimination

AUSTEDO is primarily renally eliminated in the form of metabolites.

The half-life of total (α+β)-HTBZ from deutetrabenazine is approximately 9 to 10 hours.

The median clearance values (CL/F) of the α-HTBZ, and the β-HTBZ metabolites of AUSTEDO are approximately 47 L/hour and 70 L/hour, respectively, in the Huntington’s disease patient population.

Metabolism

In vitro experiments in human liver microsomes demonstrate that deutetrabenazine is extensively biotransformed, mainly by carbonyl reductase, to its major active metabolites, α-HTBZ and β-HTBZ, which are subsequently metabolized primarily by CYP2D6, with minor contributions of CYP1A2 and CYP3A4/5, to form several minor metabolites.

Excretion

In a mass balance study in 6 healthy subjects, 75% to 86% of the deutetrabenazine dose was excreted in the urine, and fecal recovery accounted for 8% to 11% of the dose. Urinary excretion of the α-HTBZ and β-HTBZ metabolites from deutetrabenazine each accounted for less than 10% of the administered dose. Sulfate and glucuronide conjugates of the α-HTBZ and β-HTBZ metabolites of deutetrabenazine, as well as products of oxidative metabolism, accounted for the majority of metabolites in the urine.

Specific Populations

Male and Female Patients

There is no apparent effect of gender on the pharmacokinetics of α-HTBZ and β‑HTBZ of deutetrabenazine.

Patients with Renal Impairment

No clinical studies have been conducted to assess the effect of renal impairment on the PK of AUSTEDO.

Patients with Hepatic Impairment

The effect of hepatic impairment on the pharmacokinetics of deutetrabenazine and its primary metabolites has not been studied. However, in a clinical study conducted to assess the effect of hepatic impairment on the pharmacokinetics of tetrabenazine, a closely related VMAT2 inhibitor, the exposure to α-HTBZ and β-HTBZ was up to 40% greater in patients with hepatic impairment, and the mean tetrabenazine Cmax in patients with hepatic impairment was up to 190-fold higher than in healthy subjects [see Contraindications (4), Use in Specific Populations (8.6)].

Poor CYP2D6 Metabolizers

Although the pharmacokinetics of deutetrabenazine and its metabolites have not been systematically evaluated in patients who do not express the drug metabolizing enzyme CYP2D6, it is likely that the exposure to α-HTBZ and β-HTBZ would be increased similarly to taking strong CYP2D6 inhibitors (approximately 3-fold) [see Dosage and Administration (2.4), Drug Interactions (7.1)].

Drug Interaction Studies

Deutetrabenazine, α-HTBZ, and β-HTBZ have not been evaluated in in vitro studies for induction or inhibition of CYP enzymes or interaction with P-glycoprotein. The results of in vitro studies of tetrabenazine do not suggest that tetrabenazine or its α-HTBZ or β-HTBZ metabolites are likely to result in clinically significant inhibition of CYP2D6, CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2E1, or CYP3A. In vitro studies suggest that neither tetrabenazine nor its α-HTBZ or β-HTBZ metabolites are likely to result in clinically significant induction of CYP1A2, CYP3A4, CYP2B6, CYP2C8, CYP2C9, or CYP2C19. Neither tetrabenazine nor its α-HTBZ or β-HTBZ metabolites are likely to be a substrate or inhibitor of P-glycoprotein at clinically relevant concentrations in vivo.

The deutetrabenazine metabolites, 2-methylpropanoic acid of β-HTBZ (M1) and monohydroxy tetrabenazine (M4), have been evaluated in a panel of in vitro drug-drug interaction studies; the results indicate that M1/M4 are not expected to cause clinically relevant drug interactions.

CYP2D6 Inhibitors

In vitro studies indicate that the α-HTBZ and β-HTBZ metabolites of deutetrabenazine are substrates for CYP2D6. The effect of CYP2D6 inhibition on the pharmacokinetics of deutetrabenazine and its metabolites was studied in 24 healthy subjects following a single 22.5 mg dose of deutetrabenazine given after 8 days of administration of the strong CYP2D6 inhibitor paroxetine 20 mg daily. In the presence of paroxetine, systemic exposure (AUCinf ) of α-HTBZ was 1.9-fold higher and β-HTBZ was 6.5-fold higher, resulting in approximately 3-fold increase in AUCinf for total (α+β)-HTBZ. Paroxetine decreased the clearance of α-HTBZ and β-HTBZ metabolites of AUSTEDO with corresponding increases in mean half-life of approximately 1.5-fold and 2.7-fold, respectively. In the presence of paroxetine, Cmax of α-HTBZ and β-HTBZ were 1.2-fold and 2.2-fold higher, respectively.

The effect of moderate or weak CYP2D6 inhibitors such as duloxetine, terbinafine, amiodarone, or sertraline on the exposure of deutetrabenazine and its metabolites has not been evaluated.

Digoxin

AUSTEDO was not evaluated for interaction with digoxin. Digoxin is a substrate for P-glycoprotein. A study in healthy subjects showed that tetrabenazine (25 mg twice daily for 3 days) did not affect the bioavailability of digoxin, suggesting that at this dose, tetrabenazine does not affect P‑glycoprotein in the intestinal tract. In vitro studies also do not suggest that tetrabenazine or its metabolites are P-glycoprotein inhibitors.

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis

No carcinogenicity studies were performed with deutetrabenazine.

No increase in tumors was observed in p53+/– transgenic mice treated orally with tetrabenazine at doses of 0, 5, 15, and 30 mg/kg/day for 26 weeks.

Mutagenesis

Deutetrabenazine and its deuterated α-HTBZ and β-HTBZ metabolites were negative in in vitro (bacterial reverse mutation and chromosome aberration in human peripheral blood lymphocytes) assays in the presence or absence of metabolic activation and in the in vivo micronucleus assay in mice.

Impairment of Fertility

The effects of deutetrabenazine on fertility have not been evaluated. Oral administration of deutetrabenazine (doses of 5, 10, or 30 mg/kg/day) to female rats for 3 months resulted in estrous cycle disruption at all doses; the lowest dose tested was similar to the maximum recommended human dose (48 mg/day) on a body surface area (mg/m2) basis.

Oral administration of tetrabenazine (doses of 5, 15, or 30 mg/kg/day) to female rats prior to and throughout mating, and continuing through day 7 of gestation, resulted in disrupted estrous cyclicity at doses greater than 5 mg/kg/day. No effects on mating and fertility indices or sperm parameters (motility, count, density) were observed when males were treated orally with tetrabenazine at doses of 5, 15 or 30 mg/kg/day prior to and throughout mating with untreated females.

14 CLINICAL STUDIES

14.1 Chorea Associated with Huntington’s Disease

Double-Blind, Placebo-Controlled Study

The efficacy of AUSTEDO as a treatment for chorea associated with Huntington’s disease was established primarily in Study 1, a randomized, double-blind, placebo-controlled, multi-center trial conducted in 90 ambulatory patients with manifest chorea associated with Huntington’s disease. The diagnosis of Huntington’s disease was based on family history, neurological exam, and genetic testing. Treatment duration was 12 weeks, including an 8-week dose titration period and a 4-week maintenance period, followed by a 1-week washout. Patients were not blinded to discontinuation. AUSTEDO was started at 6 mg per day and titrated upward, at weekly intervals, in 6 mg increments until satisfactory treatment of chorea was achieved, intolerable side effects occurred, or until a maximal dose of 48 mg per day was reached. The primary efficacy endpoint was the Total Maximal Chorea Score, an item of the Unified Huntington’s Disease Rating Scale (UHDRS). On this scale, chorea is rated from 0 to 4 (with 0 representing no chorea) for 7 different parts of the body. The total score ranges from 0 to 28.

Of the 90 patients enrolled, 87 patients completed the study. The mean age was 54 (range 23 to 74). Patients were 56% male and 92% Caucasian. The mean dose after titration was 40 mg per day. Table 4 and Figure 1 summarize the effects of AUSTEDO on chorea based on the Total Maximal Chorea Score. Total Maximal Chorea Scores for patients receiving AUSTEDO improved by approximately 4.4 units from baseline to the maintenance period (average of Week 9 and Week 12), compared to approximately 1.9 units in the placebo group. The treatment effect of -2.5 units was statistically significant (p<0.0001). The Maintenance Endpoint is the mean of the Total Maximal Chorea Scores for the Week 9 and Week 12 visits. At the Week 13 follow-up visit (1 week after discontinuation of the study medication), the Total Maximal Chorea Scores of patients who had received AUSTEDO returned to baseline (Figure 1).

Table 4: Change from Baseline to Maintenance Therapy in Total Maximal Chorea (TMC)* Score in Patients with Huntington’s Disease Treated with AUSTEDO in Study 1
Motor Endpoint AUSTEDON = 45 Placebo N = 45 p value

Change in Total Chorea Score* from Baseline to Maintenance Therapy

-4.4

-1.9

<0.0001

* TMC is a subscale of the Unified Huntington’s Disease Rating Scale (UHDRS) Primary efficacy endpoint

Figure 1: Total Maximal Chorea Score Over Time in Study 1

figure-01.jpg
(click image for full-size original)

Figure 2: Distribution of the Change in Total Maximal Chorea Scores in Study 1

figure-02.jpg
(click image for full-size original)

Figure 2 shows the distribution of values for the change in Total Maximal Chorea Score in Study 1. Negative values indicate a reduction in chorea and positive numbers indicate an increase in chorea.

A patient-rated global impression of change assessed how patients rated their overall Huntington’s disease symptoms. Fifty-one percent of patients treated with AUSTEDO rated their symptoms as “Much Improved” or “Very Much Improved” at the end of treatment, compared to 20% of placebo-treated patients.

In a physician-rated clinical global impression of change, physicians rated 42% percent of patients treated with AUSTEDO as “Much Improved” or “Very Much Improved” at the end of treatment compared to 13% of placebo-treated patients.

DrugInserts.com provides trustworthy package insert and label information about marketed drugs as submitted by manufacturers to the US Food and Drug Administration. Package information is not reviewed or updated separately by DrugInserts.com. Every individual package label entry contains a unique identifier which can be used to secure further details directly from the US National Institutes of Health and/or the FDA.

As the leading independent provider of trustworthy medication information, we source our database directly from the FDA's central repository of drug labels and package inserts under the Structured Product Labeling standard. Our material is not intended as a substitute for direct consultation with a qualified health professional.

Terms of Use | Copyright © 2022. All Rights Reserved.