Rufinamide 400 mg Tablet, Film Coated, 120-count — NDC 31722-599-12 (Billing 31722-0599-12)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action The precise mechanism(s) by which rufinamide exerts its antiepileptic effect is unknown. The results of in vitro studies suggest that the principal mechanism of action of rufinamide is modulation of the activity of sodium channels and, in particular, prolongation of the inactive state of the channel. Rufinamide (≥ 1 µM) significantly slowed sodium channel recovery from inactivation after a prolonged prepulse in cultured cortical neurons, and limited sustained repetitive firing of sodium-dependent action potentials (EC 50 of 3.8 µM).

12.3Pharmacokinetics Overview Rufinamide is well absorbed after oral administration. However, the rate of absorption is relatively slow and the extent of absorption is decreased as dose is increased. The pharmacokinetics does not change with multiple dosing.

Most elimination of rufinamide is via metabolism, with the primary metabolite resulting from enzymatic hydrolysis of the carboxamide moiety to form the carboxylic acid. This metabolic route is not cytochrome P450 dependent. There are no known active metabolites.

Plasma half-life of rufinamide is approximately 6 to 10 hours. Absorption and Distribution Following oral administration of rufinamide, peak plasma concentrations occur between 4 and 6 hours (T max ) both under fed and fasted conditions. Rufinamide tablets display decreasing bioavailability with increasing dose after single and multiple dose administration.

Based on urinary excretion, the extent of absorption was at least 85% following oral administration of a single dose of 600 mg rufinamide tablet under fed conditions. Multiple dose pharmacokinetics can be predicted from single dose data for both rufinamide and its metabolite. Given the dosing frequency of every 12 hours and the half-life of 6 to 10 hours, the observed steady-state peak concentration of about two to three times the peak concentration after a single dose is expected.

Food increased the extent of absorption of rufinamide in healthy volunteers by 34% and increased peak exposure by 56% after a single dose of 400 mg tablet, although the T max was not elevated [see Dosage and Administration (2.2)]. Only a small fraction of rufinamide (34%) is bound to human serum proteins, predominantly to albumin (27%), giving little risk of displacement drug-drug interactions. Rufinamide was evenly distributed between erythrocytes and plasma.

The apparent volume of distribution is dependent upon dose and varies with body surface area. The apparent volume of distribution was about 50 L at 3200 mg per day. Metabolism Rufinamide is extensively metabolized but has no active metabolites.

Following a radiolabeled dose of rufinamide, less than 2% of the dose was recovered unchanged in urine. The primary biotransformation pathway is carboxylesterase(s) mediated hydrolysis of the carboxamide group to the acid derivative CGP 47292. A few minor additional metabolites were detected in urine, which appeared to be acyl-glucuronides of CGP 47292.

There is no involvement of oxidizing cytochrome P450 enzymes or glutathione in the biotransformation process. Rufinamide is a weak inhibitor of CYP 2E1. It did not show significant inhibition of other CYP enzymes.

Rufinamide is a weak inducer of CYP 3A4 enzymes. Rufinamide did not show any significant inhibition of P-glycoprotein in an in vitro study. Elimination/Excretion Renal excretion is the predominant route of elimination for drug related material, accounting for 85% of the dose based on a radiolabeled study.

Of the metabolites identified in urine, at least 66% of the rufinamide dose was excreted as the acid metabolite CGP 47292, with 2% of the dose excreted as rufinamide. The plasma elimination half-life is approximately 6 to 10 hours in healthy subjects and patients with epilepsy. Special Populations Age • Pediatrics Based on a population analysis which included a total of 115 patients, including 85 pediatric patients (24 patients ages 1 to 3 years, 40… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action The precise mechanism(s) by which rufinamide exerts its antiepileptic effect is unknown. The results of in vitro studies suggest that the principal mechanism of action of rufinamide is modulation of the activity of sodium channels and, in particular, prolongation of the inactive state of the channel. Rufinamide (≥ 1 µM) significantly slowed sodium channel recovery from inactivation after a prolonged prepulse in cultured cortical neurons, and limited sustained repetitive firing of sodium-dependent action potentials (EC 50 of 3.8 µM).

12.3Pharmacokinetics Overview Rufinamide is well absorbed after oral administration. However, the rate of absorption is relatively slow and the extent of absorption is decreased as dose is increased. The pharmacokinetics does not change with multiple dosing.

Most elimination of rufinamide is via metabolism, with the primary metabolite resulting from enzymatic hydrolysis of the carboxamide moiety to form the carboxylic acid. This metabolic route is not cytochrome P450 dependent. There are no known active metabolites.

Plasma half-life of rufinamide is approximately 6 to 10 hours. Absorption and Distribution Following oral administration of rufinamide, peak plasma concentrations occur between 4 and 6 hours (T max ) both under fed and fasted conditions. Rufinamide tablets display decreasing bioavailability with increasing dose after single and multiple dose administration.

Based on urinary excretion, the extent of absorption was at least 85% following oral administration of a single dose of 600 mg rufinamide tablet under fed conditions. Multiple dose pharmacokinetics can be predicted from single dose data for both rufinamide and its metabolite. Given the dosing frequency of every 12 hours and the half-life of 6 to 10 hours, the observed steady-state peak concentration of about two to three times the peak concentration after a single dose is expected.

Food increased the extent of absorption of rufinamide in healthy volunteers by 34% and increased peak exposure by 56% after a single dose of 400 mg tablet, although the T max was not elevated [see Dosage and Administration (2.2)]. Only a small fraction of rufinamide (34%) is bound to human serum proteins, predominantly to albumin (27%), giving little risk of displacement drug-drug interactions. Rufinamide was evenly distributed between erythrocytes and plasma.

The apparent volume of distribution is dependent upon dose and varies with body surface area. The apparent volume of distribution was about 50 L at 3200 mg per day. Metabolism Rufinamide is extensively metabolized but has no active metabolites.

Following a radiolabeled dose of rufinamide, less than 2% of the dose was recovered unchanged in urine. The primary biotransformation pathway is carboxylesterase(s) mediated hydrolysis of the carboxamide group to the acid derivative CGP 47292. A few minor additional metabolites were detected in urine, which appeared to be acyl-glucuronides of CGP 47292.

There is no involvement of oxidizing cytochrome P450 enzymes or glutathione in the biotransformation process. Rufinamide is a weak inhibitor of CYP 2E1. It did not show significant inhibition of other CYP enzymes.

Rufinamide is a weak inducer of CYP 3A4 enzymes. Rufinamide did not show any significant inhibition of P-glycoprotein in an in vitro study. Elimination/Excretion Renal excretion is the predominant route of elimination for drug related material, accounting for 85% of the dose based on a radiolabeled study.

Of the metabolites identified in urine, at least 66% of the rufinamide dose was excreted as the acid metabolite CGP 47292, with 2% of the dose excreted as rufinamide. The plasma elimination half-life is approximately 6 to 10 hours in healthy subjects and patients with epilepsy. Special Populations Age • Pediatrics Based on a population analysis which included a total of 115 patients, including 85 pediatric patients (24 patients ages 1 to 3 years, 40 patients ages 4 to 11 years, and 21 patients ages 12 to 17 years), the pharmacokinetics of rufinamide was similar across all age groups. • Elderly The results of a study evaluating single-dose (400 mg) and multiple dose (800 mg per day for 6 days) pharmacokinetics of rufinamide in 8 healthy elderly subjects (65 to 80 years old) and 7 younger healthy subjects (18 to 45 years old) found no significant age-related differences in the pharmacokinetics of rufinamide.

Sex Population pharmacokinetic analyses of females show a 6 to 14% lower apparent clearance of rufinamide compared to males… [Excerpted — this section continues on DailyMed.]

14 CLINICAL STUDIES Adult and Pediatric Patients ages 4 years and older The effectiveness of rufinamide as adjunctive treatment for the seizures associated with Lennox-Gastaut Syndrome (LGS) in adult and pediatric patients ages 4 years and older was established in a single multicenter, double-blind, placebo-controlled, randomized, parallel-group study (N=138). Male and female patients (between 4 and 30 years of age) were included if they had a diagnosis of inadequately controlled seizures associated with LGS (including both atypical absence seizures and drop attacks) and were being treated with 1 to 3 concomitant stable dose AEDs.

Each patient must have had at least 90 seizures in the month prior to study entry. After completing a 4-week Baseline Phase on stable therapy, patients were randomized to have rufinamide or placebo added to their ongoing therapy during the 12- week Double-blind Phase. The Double-blind Phase consisted of 2 periods: the Titration Period (1 to 2 weeks) and the Maintenance Period (10 weeks).

During the Titration Period, the dose was increased to a target dosage of approximately 45 mg/kg per day (3200 mg in adults of ≥ 70 kg), given on a twice daily schedule. Dosage reductions were permitted during titration if problems in tolerability were encountered. Final doses at titration were to remain stable during the maintenance period.

Target dosage was achieved in 88% of the rufinamide-treated patients. The majority of these patients reached the target dose within 7 days, with the remaining patients achieving the target dose within 14 days. The primary efficacy variables were: • The percent change in total seizure frequency per 28 days; • The percent change in tonic-atonic (drop attacks) seizure frequency per 28 days; • Seizure severity from the Parent/Guardian Global Evaluation of the patient’s condition.

This was a 7-point assessment performed at the end of the Double-blind Phase. A score of +3 indicated that the patient’s seizure severity was very much improved, a score of 0 that the seizure severity was unchanged, and a score of -3 that the seizure severity was very much worse. The results of the three primary endpoints are shown in Table 7 below.

Table 7: Lennox-Gastaut Syndrome Trial Seizure Frequency Primary Efficacy Variable Results Variable Placebo Rufinamide Median percent change in total seizure frequency per 28 days -11.7 -32.7 (p=0.0015) Median percent change in tonic-atonic seizure frequency per 28 days 1.4 -42.5 (p<0.0001) Improvement in Seizure Severity Rating from Global Evaluation 30.6 53.4 (p=0.0041) Pediatric Patients ages 1 to less than 4 years The effectiveness of rufinamide as adjunctive treatment for the seizures associated with Lennox-Gastaut Syndrome in pediatric patients ages 1 year to less than 4 years was established based on a single multi-center, open-label, active-controlled, randomized, pharmacokinetic bridging study.

The pharmacokinetic profile of rufinamide is not significantly affected by age either as a continuous covariate (1 to 35 years) or as a categorical covariate (age categories: 1 to less than 4 years and 4 years of age and older), after body weight is taken into consideration.

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis Rufinamide was given in the diet to mice at 40, 120, and 400 mg/kg per day and to rats at 20, 60, and 200 mg/kg per day for 2 years. The doses in mice were associated with plasma AUCs 0.1 to 1 times the human plasma AUC at the maximum recommended human dose (MRHD, 3200 mg/day). Increased incidences of tumors (benign bone tumors (osteomas) and/or hepatocellular adenomas and carcinomas) were observed in mice at all doses.

Increased incidences of thyroid follicular adenomas were observed in rats at all but the low dose; the low dose is <0.1 times the MRHD on a mg/m 2 basis. Mutagenesis Rufinamide was not mutagenic in the in vitro bacterial reverse mutation (Ames) assay or the in vitro mammalian cell point mutation assay. Rufinamide was not clastogenic in the in vitro mammalian cell chromosomal aberration assay or the in vivo rat bone marrow micronucleus assay.

Impairment of Fertility Oral administration of rufinamide (doses of 20, 60, 200, and 600 mg/kg per day) to male and female rats prior to mating and throughout mating, and continuing in females up to day 6 of gestation resulted in impairment of fertility (decreased conception rates and mating and fertility indices; decreased numbers of corpora lutea, implantations, and live embryos; increased preimplantation loss; decreased sperm count and motility) at all doses tested. Therefore, a no-effect dose was not established.

The lowest dose tested was associated with a plasma AUC ≈ 0.2 times the human plasma AUC at the MRHD.