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Azilect

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Azilect

CLINICAL PHARMACOLOGY

Mechanism Of Action

AZILECT is a selective, irreversible MAO-B inhibitor indicated for the treatment of idiopathic Parkinson's disease. The results of a clinical trial designed to examine the effects of AZILECT on blood pressure when it is administered with increasing doses of tyramine indicates the functional selectivity can be incomplete when healthy subjects ingest large amounts of tyramine while receiving recommended doses of AZILECT. The selectivity for inhibiting MAO-B diminishes in a dose-related manner.

MAO, a flavin-containing enzyme, is classified into two major molecular species, A and B, and is localized in mitochondrial membranes throughout the body in nerve terminals, brain, liver and intestinal mucosa. MAO regulates the metabolic degradation of catecholamines and serotonin in the CNS and peripheral tissues. MAO-B is the major form in the human brain. In ex vivo animal studies in brain, liver, and intestinal tissues, rasagiline was shown to be a potent, irreversible monoamine oxidase type B (MAO-B) selective inhibitor. Rasagiline at the recommended therapeutic dose was also shown to be a potent and irreversible inhibitor of MAO-B in platelets. The precise mechanisms of action of rasagiline are unknown. One mechanism is believed to be related to its MAO-B inhibitory activity, which causes an increase in extracellular levels of dopamine in the striatum. The elevated dopamine level and subsequent increased dopaminergic activity are likely to mediate rasagiline's beneficial effects seen in models of dopaminergic motor dysfunction.

Pharmacodynamics

Tyramine Challenge Test

Results of a tyramine challenge study indicate that rasagiline at recommended doses is relatively selective for inhibiting MAO-B and can be used without dietary tyramine restriction. However, certain foods (e.g., aged cheeses, such as Stilton cheese) may contain very high amounts of tyramine (i.e., 150 mg or greater) and could potentially cause severe hypertension caused by tyramine interaction in patients taking AZILECT due to mild increased sensitivity to tyramine at recommended doses. Relative selectivity of AZILECT for inhibiting MAO-B diminished in a dose-related manner as the dose progressively increased above the highest recommended daily dose (1 mg) [see WARNINGS AND PRECAUTIONS and DRUG INTERACTIONS].

Platelet MAO Activity in Clinical Studies

Studies in healthy subjects and in Parkinson's disease patients have shown that rasagiline inhibits platelet MAO-B irreversibly. The inhibition lasts at least 1 week after last dose. Almost 25-35% MAO-B inhibition was achieved after a single rasagiline dose of 1 mg/day and more than 55% of MAO-B inhibition was achieved after a single rasagiline dose of 2 mg/day. Over 90% inhibition was achieved 3 days after rasagiline daily dosing at 2 mg/day and this inhibition level was maintained 3 days postdose. Multiple doses of rasagiline of 0.5, 1 and 2 mg per day resulted in complete MAO-B inhibition.

Pharmacokinetics

Rasagiline in the range of 1-6 mg demonstrated a more than proportional increase in AUC, while Cmax was dose proportional. Rasagiline mean steady-state half life is 3 hours but there is no correlation of pharmacokinetics with its pharmacological effect because of its irreversible inhibition of MAO-B.

Absorption

Rasagiline is rapidly absorbed, reaching peak plasma concentration (Cmax) in approximately 1 hour. The absolute bioavailability of rasagiline is about 36%.

Food does not affect the Tmax of rasagiline, although Cmax and exposure (AUC) are decreased by approximately 60% and 20%, respectively, when the drug is taken with a high fat meal. Because AUC is not significantly affected, AZILECT can be administered with or without food.

Distribution

The mean volume of distribution at steady-state is 87 L, indicating that the tissue binding of rasagiline is in excess of plasma protein binding. Plasma protein binding ranges from 88-94% with mean extent of binding of 61-63% to human albumin over the concentration range of 1-100 ng/mL.

Metabolism and Elimination

Rasagiline undergoes almost complete biotransformation in the liver prior to excretion. The metabolism of rasagiline proceeds through two main pathways: N-dealkylation and/or hydroxylation to yield 1-aminoindan (AI), 3-hydroxy-N-propargyl-1 aminoindan (3-OH-PAI) and 3-hydroxy-1-aminoindan (3-OH-AI). In vitro experiments indicate that both routes of rasagiline metabolism are dependent on the cytochrome P450 (CYP) system, with CYP1A2 being the major isoenzyme involved in rasagiline metabolism. Glucuronide conjugation of rasagiline and its metabolites, with subsequent urinary excretion, is the major elimination pathway.

After oral administration of 14C-labeled rasagiline, elimination occurred primarily via urine and secondarily via feces (62% of total dose in urine and 7% of total dose in feces over 7 days), with a total calculated recovery of 84% of the dose over a period of 38 days. Less than 1% of rasagiline was excreted as unchanged drug in urine.

Special Populations

Hepatic Impairment

Following repeat dose administration (7 days) of rasagiline (1 mg/day) in subjects with mild hepatic impairment (Child-Pugh score 5-6), AUC and Cmax were increased by 2 fold and 1.4 fold, respectively, compared to healthy subjects. In subjects with moderate hepatic impairment (Child-Pugh score 7-9), AUC and Cmax were increased by 7 fold and 2 fold, respectively, compared to healthy subjects [see DOSAGE AND ADMINISTRATION and WARNINGS AND PRECAUTIONS].

Renal Impairment

Following repeat dose administration (8 days) of rasagiline (1 mg/day) in subjects with moderate renal impairment, rasagiline exposure (AUC) was similar to rasagiline exposure in healthy subjects, while the major metabolite 1-AI exposure (AUC) was increased 1.5-fold in subjects with moderate renal impairment, compared to healthy subjects. Because 1-AI is not an MAO inhibitor, no dose adjustment is needed for patients with mild and moderate renal impairment. Data are not available for patients with severe renal impairment.

Elderly

Since age has little influence on rasagiline pharmacokinetics, it can be administered at the recommended dose in the elderly (≥ 65 years).

Pediatric

AZILECT has not been investigated in patients below 18 years of age.

Gender

The pharmacokinetic profile of rasagiline is similar in men and women.

Drug-Drug Interactions

Levodopa

A study in Parkinson's disease patients, in which the effect of levodopa/carbidopa (LD/CD) on rasagiline pharmacokinetics at steady state was investigated, showed that the pharmacokinetics of rasagiline were not affected by concomitant administration of LD/CD.

Effect of Other Drugs on the Metabolism of AZILECT

In vitro metabolism studies showed that CYP1A2 was the major enzyme responsible for the metabolism of rasagiline. There is the potential for inhibitors of this enzyme to alter AZILECT clearance when coadministered [see DOSAGE AND ADMINISTRATION and WARNINGS AND PRECAUTIONS].

Ciprofloxacin: When ciprofloxacin, an inhibitor of CYP1A2, was administered to healthy volunteers (n=12) at 500 mg (BID) with rasagiline at 2 mg/day, the AUC of rasagiline increased by 83% and there was no change in the elimination half life [see DOSAGE AND ADMINISTRATION and WARNINGS AND PRECAUTIONS].

Theophylline: Coadministration of rasagiline 1 mg/day and theophylline, a substrate of CYP1A2, up to 500 mg twice daily to healthy subjects (n=24) did not affect the pharmacokinetics of either drug.

Antidepressants: Severe CNS toxicity (occasionally fatal) associated with hyperpyrexia as part of a serotonin syndrome, has been reported with combined treatment of an antidepressant (e.g., from one of many classes including tricyclic or tetracyclic antidepressants, SSRIs, SNRIs, triazolopyridine antidepressants) and nonselective MAOI or a selective MAO-B inhibitor [see WARNINGS AND PRECAUTIONS].

Effect of AZILECT on Other Drugs

No additional in vivo trials have investigated the effect of AZILECT on other drugs metabolized by the cytochrome P450 enzyme system. In vitro studies showed that rasagiline at a concentration of 1 mcg/ml (equivalent to a level that is 160 times the average Cmax ~ 5.9-8.5 ng/mL in Parkinson's disease patients after 1 mg rasagiline multiple dosing) did not inhibit cytochrome P450 isoenzymes, CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4 and CYP4A. These results indicate that rasagiline is unlikely to cause any clinically significant interference with substrates of these enzymes.

Clinical Studies

The effectiveness of AZILECT for the treatment of Parkinson's disease was established in four 18-to 26-week, randomized, placebo-controlled trials, as initial monotherapy or adjunct therapy.

Monotherapy Use Of AZILECT

Study 1 was a double-blind, randomized, fixed-dose parallel group, 26-week study in early Parkinson's disease patients not receiving any concomitant dopaminergic therapy at the start of the study. The majority of the patients were not treated with medications for Parkinson's disease before receiving AZILECT.

In Study 1, 404 patients were randomly assigned to receive placebo (138 patients), AZILECT 1 mg/day (134 patients) or AZILECT 2 mg/day (132 patients). Patients were not allowed to take levodopa, dopamine agonists, selegiline or amantadine, but could take stable doses of anticholinergic medication, if necessary. The average Parkinson's disease duration was approximately 1 year (range 0 to 11 years).

The primary measure of effectiveness was the change from baseline in the total score of the Unified Parkinson's Disease Rating Scale (UPDRS), [mentation (Part I) + activities of daily living (ADL) (Part II) + motor function (Part III)]. The UPDRS is a multi-item rating scale that measures the ability of a patient to perform mental and motor tasks as well as activities of daily living. A reduction in the score represents improvement and a beneficial change from baseline appears as a negative number.

AZILECT (1 or 2 mg once daily) was superior to placebo on the primary measure of effectiveness in patients receiving six months of treatment and not on dopaminergic therapy. The effectiveness of AZILECT 1 mg and 2 mg was comparable. Table 4 shows the results of Study 1. There were no differences in effectiveness based on age or gender between AZILECT 1 mg/day and placebo.

Table 4: Change in Total UPDRS Score in Study 1

  Baseline score Change from baseline to termination score p-value vs. placebo
Placebo 24.5 3.9
AZILECT 1 mg 24.7 0.1 0.0001
AZILECT 2 mg 25.9 0.7 0.0001

Adjunct Use Of AZILECT

Study 2 was a double-blind, randomized, placebo-controlled, parallel group, 18-week study, investigating AZILECT 1 mg as adjunct therapy to dopamine agonists without levodopa. Patients were on a stable dose of dopamine agonist (ropinirole, mean 8 mg/day or pramipexole, mean 1.5 mg/day) therapy for ≥ 30 days, but at doses not sufficient to control Parkinson's disease symptoms.

In Study 2, 321 patients randomly received placebo (162 patients) or AZILECT 1 mg/day (159 patients) and had a post-baseline assessment. The average Parkinson's disease duration was approximately 2 years (range 0.1 to 14.5 years).

The primary measure of effectiveness was the change from baseline in the total score of the Unified Parkinson's Disease Rating Scale (UPDRS) [mentation (Part I) + activities of daily living (ADL) (Part II) + motor function (Part III)].

In Study 2, AZILECT 1 mg was superior to placebo on the primary measure of effectiveness (see Table 5).

Table 5: Change in Total UPDRS Score in Study 2

  Baseline score Change from baseline to termination score* p-value vs. placebo
Placebo 29.8 -1.2
AZILECT1 mg 32.1 -3.6 0.012
*A negative change from baseline indicates improvement in the UPDRS

Secondary outcome assessment of the individual subscales of the UPDRS indicates that the UPDRS Part III motor subscale was primarily responsible for the overall AZILECT effect on the UPDRS score (see Table 6).

Table 6: Secondary Measures of Effectiveness in Study 2

  Baseline (score) Change from baseline to termination score
UPDRS Part IIADL (Activities of Daily Living) subscale score
Placebo 7.9 0.4
AZILECT 1 mg 8.6 -0.3
UPDRS Part III Motor subscale score
Placebo 20.4 -1.2
AZILECT 1 mg 22.2 -3.7

Study 3 and Study 4 were randomized, multinational trials conducted in more advanced Parkinson's disease patients treated chronically with levodopa and experiencing motor fluctuations (including but not limited to, end of dose “wearing off,” sudden or random “off,” etc.). Study 3 was conducted in North America (U.S. and Canada) and compared AZILECT 0.5 mg and 1 mg daily to placebo. Study 4 was conducted outside of North America in Europe, Argentina and Israel, and compared AZILECT 1 mg daily to placebo.

Patients had Parkinson's disease for an average of 9 years (range 5 months to 33 years), had taken levodopa for an average of 8 years (range 5 months to 32 years), and had motor fluctuations for approximately 3 to 4 years (range 1 month to 23 years). Patients kept home Parkinson's disease diaries just prior to baseline and at specified intervals during the trial. Diaries recorded one of the following four conditions for each half-hour interval over a 24-hour period: “ON” (period of relatively good function and mobility) as either “ON” with no dyskinesia or without troublesome dyskinesia, or “ON” with troublesome dyskinesia, “OFF” (period of relatively poor function and mobility) or asleep. “Troublesome” dyskinesia is defined as dyskinesia that interferes with the patient's daily activity. All patients had inadequate control of their motor symptoms with motor fluctuations typical of advanced stage disease despite receiving levodopa/decarboxylase inhibitor. The average dose of levodopa taken with a decarboxylase inhibitor was approximately 700 to 800 mg (range 150 to 3000 mg/day). Patients continued their stable doses of additional anti-PD medications at entry into the trials. Approximately 65% of patients in both studies were also taking a dopamine agonist. In the North American study (Study 3), approximately 35% of patients took entacapone with levodopa/decarboxylase inhibitor. The majority of patients taking entacapone were also taking a dopamine agonist.

In Study 3 and Study 4, the primary measure of effectiveness was the change in the mean number of hours spent in the “OFF” state at baseline compared to the mean number of hours spent in the “OFF” state during the treatment period.

In Study 3, patients were randomly assigned to receive placebo (159 patients), AZILECT 0.5 mg/day (164 patients), or AZILECT 1 mg/day (149 patients) for 26 weeks. Patients averaged 6 hours daily in the “OFF” state at baseline as confirmed by home diaries.

In Study 4, patients were randomly assigned to receive placebo (229 patients), AZILECT 1 mg/day (231 patients) or a COMT inhibitor (active comparator), taken along with scheduled doses of levodopa/decarboxylase inhibitor (227 patients) for 18 weeks. Patients averaged 5.6 hours daily in the “OFF” state at baseline as confirmed by home diaries.

In Study 3 and Study 4, AZILECT 1 mg once daily reduced “OFF” time compared to placebo when added to levodopa in patients experiencing motor fluctuations (Tables 7 and 8). The lower dose (0.5 mg) of AZILECT also significantly reduced “OFF” time (Table 7), but had a numerically smaller effect than the 1 mg dose of AZILECT. In Study 4, the active comparator also reduced “OFF” time when compared to placebo.

Table 7: Change in mean total daily “OFF” time in Study 3

  Baseline (hours) Change from baseline to treatment period (hours) p-value vs. placebo
Placebo 6.0 -0.9
AZILECT 0.5 mg 6.0 -1.4 0.0199
AZILECT 1.0 mg 6.3 -1.9 < 0.0001

Table 8: Change in mean total daily “OFF” time in Study 4

  Baseline (hours) Change from baseline to treatment period (hours) p-value vs. placebo
Placebo 5.5 -0.40
AZILECT 1.0 mg 5.6 -1.2 0.0001

In Study 3 and Study 4, dose reduction of levodopa was allowed within the first 6 weeks, if dopaminergic side effects developed including dyskinesia or hallucinations. In Study 3, the levodopa dose was reduced in 8% of patients in the placebo group and in 16% and 17% of patients in the 0.5 mg/day and 1 mg/day AZILECT groups, respectively. When levodopa was reduced, the dose was reduced by 7%, 9%, and 13% in the placebo, 0.5 mg/day, and 1 mg/day groups, respectively. In Study 4, levodopa dose reduction occurred in 6% of patients in the placebo group and in 9% in the AZILECT 1 mg/day groups, respectively. When levodopa was reduced, it was reduced by 13% and 11% in the placebo and the AZILECT groups, respectively.

There were no differences in effectiveness based on age or gender between AZILECT 1 mg/day and placebo.

Several secondary outcome assessments in the two studies showed statistically significant improvements with rasagiline. These included effects on the activities of daily living (ADL) subscale of the UPDRS performed during an “OFF” period and the motor subscale of the UPDRS performed during an “ON” period. In both scales, a negative response represents improvement. Tables 9 and 10 show these results for Studies 3 and 4.

Table 9: Secondary Measures of Effectiveness in Study 3

  Baseline (score) Change from baseline to last value
UPDRS ADL (Activities of Daily Living) subscale score while “OFF”
Placebo 15.5 0.68
AZILECT 0.5 mg 15.8 -0.60
AZILECT 1 mg 15.5 -0.68
UPDRS Motor subscale score while “ON”
Placebo 20.8 1.21
AZILECT 0.5 mg 21.5 -1.43
AZILECT 1 mg 20.9 -1.30

Table 10: Secondary Measures of Effectiveness in Study 4

  Baseline (score) Change from baseline to last value
UPDRS ADL (Activities of Daily Living) subscale score while “OFF”
Placebo 18.7 -0.89
AZILECT 1 mg 19.0 -2.61
UPDRS Motor subscale score while “ON”
Placebo 23.5 -0.82
AZILECT 1 mg 23.8 -3.87

Last reviewed on RxList: 6/12/2014
This monograph has been modified to include the generic and brand name in many instances.

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