Febuxostat 80 mg Tablet, 30-count — NDC 43547-296-03 (Billing 43547-0296-03)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action Febuxostat, a xanthine oxidase inhibitor, achieves its therapeutic effect by decreasing serum uric acid. Febuxostat is not expected to inhibit other enzymes involved in purine and pyrimidine synthesis and metabolism at therapeutic concentrations.

12.2Pharmacodynamics Effect on Uric Acid and Xanthine Concentrations In healthy patients, febuxostat resulted in a dose dependent decrease in 24-hour mean serum uric acid concentrations and an increase in 24-hour mean serum xanthine concentrations. In addition, there was a decrease in the total daily urinary uric acid excretion. Also, there was an increase in total daily urinary xanthine excretion.

Percent reduction in 24-hour mean serum uric acid concentrations was between 40% and 55% at the exposure levels of 40 mg and 80 mg daily doses. Effect on Cardiac Repolarization The effect of febuxostat on cardiac repolarization as assessed by the QTc interval was evaluated in normal healthy patients and in patients with gout. Febuxostat in doses up to 300 mg daily (3.75 times the maximum recommended daily dosage), at steady-state, did not demonstrate an effect on the QTc interval.

12.3Pharmacokinetics In healthy patients, maximum plasma concentrations (C max ) and AUC of febuxostat increased in a dose proportional manner following single and multiple doses of 10 mg (0.25 times the lowest recommended dosage) to 120 mg (1.5 times the maximum recommended dosage). There is no accumulation when therapeutic doses are administered every 24 hours. Febuxostat has an apparent mean terminal elimination half-life (t 1/2 ) of approximately 5 to 8 hours.

Febuxostat pharmacokinetic parameters for patients with hyperuricemia and gout estimated by population pharmacokinetic analyses were similar to those estimated in healthy patients. Absorption The absorption of radiolabeled febuxostat following oral dose administration was estimated to be at least 49% (based on total radioactivity recovered in urine). Maximum plasma concentrations of febuxostat occurred between 1 and 1.5 hours postdose.

After multiple oral 40 mg and 80 mg once daily doses, C max is approximately 1.6 ± 0.6 mcg/mL (N=30), and 2.6 ± 1.7 mcg/mL (N=227), respectively. Absolute bioavailability of the febuxostat tablet has not been studied. Following multiple 80 mg once daily doses with a high fat meal, there was a 49% decrease in C max and an 18% decrease in AUC, respectively.

However, no clinically significant change in the percent decrease in serum uric acid concentration was observed (58% fed vs 51% fasting). Thus, febuxostat may be taken without regard to food. Concomitant ingestion of an antacid containing magnesium hydroxide and aluminum hydroxide with an 80 mg single dose of febuxostat has been shown to delay absorption of febuxostat (approximately one hour) and to cause a 31% decrease in C max and a 15% decrease in AUC ∞ .

As AUC rather than C max was related to drug effect, change observed in AUC was not considered clinically significant. Therefore, febuxostat may be taken without regard to antacid use. Distribution The mean apparent steady state volume of distribution (V ss /F) of febuxostat was approximately 50 L (CV ~40%).

The plasma protein binding of febuxostat is approximately 99.2% (primarily to albumin), and is constant over the concentration range achieved with 40 mg and 80 mg doses. Metabolism Febuxostat is extensively metabolized by both conjugation via uridine diphosphate glucuronosyltransferase (UGT) enzymes including UGT1A1, UGT1A3, UGT1A9, and UGT2B7 and oxidation via cytochrome P450 (CYP) enzymes including CYP1A2, 2C8 and 2C9 and non-P450 enzymes. The relative contribution of each enzyme isoform in the metabolism of febuxostat is not clear.

The oxidation of the isobutyl side chain leads to the formation of four pharmacologically active hydroxy metabolites, all of which occur in plasma of humans at a much lower extent than febuxostat. In urine and feces, acyl glucuronid… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action Febuxostat, a xanthine oxidase inhibitor, achieves its therapeutic effect by decreasing serum uric acid. Febuxostat is not expected to inhibit other enzymes involved in purine and pyrimidine synthesis and metabolism at therapeutic concentrations.

12.3Pharmacokinetics In healthy patients, maximum plasma concentrations (C max ) and AUC of febuxostat increased in a dose proportional manner following single and multiple doses of 10 mg (0.25 times the lowest recommended dosage) to 120 mg (1.5 times the maximum recommended dosage). There is no accumulation when therapeutic doses are administered every 24 hours. Febuxostat has an apparent mean terminal elimination half-life (t 1/2 ) of approximately 5 to 8 hours.

Febuxostat pharmacokinetic parameters for patients with hyperuricemia and gout estimated by population pharmacokinetic analyses were similar to those estimated in healthy patients. Absorption The absorption of radiolabeled febuxostat following oral dose administration was estimated to be at least 49% (based on total radioactivity recovered in urine). Maximum plasma concentrations of febuxostat occurred between 1 and 1.5 hours postdose.

After multiple oral 40 mg and 80 mg once daily doses, C max is approximately 1.6 ± 0.6 mcg/mL (N=30), and 2.6 ± 1.7 mcg/mL (N=227), respectively. Absolute bioavailability of the febuxostat tablet has not been studied. Following multiple 80 mg once daily doses with a high fat meal, there was a 49% decrease in C max and an 18% decrease in AUC, respectively.

However, no clinically significant change in the percent decrease in serum uric acid concentration was observed (58% fed vs 51% fasting). Thus, febuxostat may be taken without regard to food. Concomitant ingestion of an antacid containing magnesium hydroxide and aluminum hydroxide with an 80 mg single dose of febuxostat has been shown to delay absorption of febuxostat (approximately one hour) and to cause a 31% decrease in C max and a 15% decrease in AUC ∞ .

As AUC rather than C max was related to drug effect, change observed in AUC was not considered clinically significant. Therefore, febuxostat may be taken without regard to antacid use. Distribution The mean apparent steady state volume of distribution (V ss /F) of febuxostat was approximately 50 L (CV ~40%).

The plasma protein binding of febuxostat is approximately 99.2% (primarily to albumin), and is constant over the concentration range achieved with 40 mg and 80 mg doses. Metabolism Febuxostat is extensively metabolized by both conjugation via uridine diphosphate glucuronosyltransferase (UGT) enzymes including UGT1A1, UGT1A3, UGT1A9, and UGT2B7 and oxidation via cytochrome P450 (CYP) enzymes including CYP1A2, 2C8 and 2C9 and non-P450 enzymes. The relative contribution of each enzyme isoform in the metabolism of febuxostat is not clear.

The oxidation of the isobutyl side chain leads to the formation of four pharmacologically active hydroxy metabolites, all of which occur in plasma of humans at a much lower extent than febuxostat. In urine and feces, acyl glucuronide metabolites of febuxostat (~35% of the dose), and oxidative metabolites, 67M-1 (~10% of the dose), 67M-2 (~11% of the dose), and 67M-4, a secondary metabolite from 67M-1 (~14% of the dose), appeared to be the major metabolites of febuxostat in vivo . Elimination Febuxostat is eliminated by both hepatic and renal pathways.

Following an 80 mg oral dose of 14 C-labeled febuxostat, approximately 49% of the dose was recovered in the urine as unchanged febuxostat (3%), the acyl glucuronide of the drug (30%), its known oxidative metabolites and their conjugates (13%), and other unknown metabolites (3%). In addition to the urinary excretion, approximately 45% of the dose was recovered in the feces as the unchanged febuxostat (12%), the acyl glucuronide of the drug (1%), its known oxidative metabolites and their conjugates (25%), and other unknown metabolites (7%).

The apparent mean terminal elimination half-life (t 1/2 ) of febuxostat was approximately 5 to 8 hours. Specific Populations Geriatric Patients The C max and AUC of febuxostat and its metabolites following multiple oral doses of febuxostat in geriatric patients (≥65 years) were similar to those in younger patients… [Excerpted — this section continues on DailyMed.]

12.2Pharmacodynamics Effect on Uric Acid and Xanthine Concentrations In healthy patients, febuxostat resulted in a dose dependent decrease in 24-hour mean serum uric acid concentrations and an increase in 24-hour mean serum xanthine concentrations. In addition, there was a decrease in the total daily urinary uric acid excretion. Also, there was an increase in total daily urinary xanthine excretion.

Percent reduction in 24-hour mean serum uric acid concentrations was between 40% and 55% at the exposure levels of 40 mg and 80 mg daily doses. Effect on Cardiac Repolarization The effect of febuxostat on cardiac repolarization as assessed by the QTc interval was evaluated in normal healthy patients and in patients with gout. Febuxostat in doses up to 300 mg daily (3.75 times the maximum recommended daily dosage), at steady-state, did not demonstrate an effect on the QTc interval.

14 CLINICAL STUDIES A serum uric acid level of less than 6 mg/dL is the goal of antihyperuricemic therapy and has been established as appropriate for the treatment of gout.

14.1Management of Hyperuricemia in Gout The efficacy of febuxostat was demonstrated in three randomized, double-blind, controlled trials in patients with hyperuricemia and gout. Hyperuricemia was defined as a baseline serum uric acid level ≥8 mg/dL. Study 1 (NCT00430248) randomized patients to: febuxostat 40 mg daily, febuxostat 80 mg daily, or allopurinol (300 mg daily for patients with estimated creatinine clearance (Cl cr ) ≥60 mL/min or 200 mg daily for patients with estimated Cl cr ≥30 mL/min and ≤59 mL/min).

The duration of Study 1 was six months. Study 2 (NCT00174915) randomized patients to: placebo, febuxostat 80 mg daily, febuxostat 120 mg daily, febuxostat 240 mg daily or allopurinol (300 mg daily for patients with a baseline serum creatinine ≤1.5 mg/dL or 100 mg daily for patients with a baseline serum creatinine greater than 1.5 mg/dL and ≤2 mg/dL). The duration of Study 2 was six months.

Study 3 (NCT00102440), a year study, randomized patients to: febuxostat 80 mg daily, febuxostat 120 mg daily, or allopurinol 300 mg daily. Patients who completed Study 2 and Study 3 were eligible to enroll in a Phase 3 long-term extension study in which patients received treatment with febuxostat for over three years. In all three studies, patients received naproxen 250 mg twice daily or colchicine 0.6 mg once or twice daily for gout flare prophylaxis.

In Study 1 the duration of prophylaxis was six months; in Study 2 and Study 3 the duration of prophylaxis was eight weeks. The efficacy of febuxostat was also evaluated in a 4-week dose ranging study which randomized patients to: placebo, febuxostat 40 mg daily, febuxostat 80 mg daily, or febuxostat 120 mg daily. Patients who completed this study were eligible to enroll in a long-term extension study in which patients received treatment with febuxostat for up to five years.

Patients in these studies were representative of the patient population for which febuxostat use is intended. Table 2 summarizes the demographics and baseline characteristics for the patients enrolled in the studies. Table 2: Patient Demographics and Baseline Characteristics in Study 1, Study 2, and Study 3 Male 95% Race: Caucasian African American 80% 10% Ethnicity: Hispanic or Latino 7% Alcohol User 67% Mild to Moderate Renal Insufficiency (percent with estimated Cl cr less than 90 mL/min) 59% History of Hypertension 49% History of Hyperlipidemia 38% BMI ≥30 kg/m 2 63% Mean BMI 33 kg/m 2 Baseline sUA ≥10 mg/dL 36% Mean baseline sUA 9.7 mg/dL Experienced a gout flare in previous year 85% Serum Uric Acid Level less than 6 mg/dL at Final Visit Febuxostat 80 mg was superior to allopurinol in lowering serum uric acid to less than 6 mg/dL at the final visit.

Febuxostat 40 mg daily, although not superior to allopurinol, was effective in lowering serum uric acid to less than 6 mg/dL at the final visit (Table 3) . Table 3: Proportion of Patients with Serum Uric Acid Levels less than 6 mg/dL at Final Visit Difference in Proportion (95% CI) Study* Febuxostat 40 mg daily Febuxostat 80 mg daily allopurinol Placebo Febuxostat 40 mg vs allopurinol Febuxostat 80 mg vs allopurinol Study 1 (6 months) (N=2268) 45% 67% 42% 3% (-2%, 8%) 25% (20%, 30%) Study 2 (6 months) (N=643) 72% 39% 1% 33% (26%, 42%) Study 3 (12 months) (N=491) 74% 36% 38% (30%, 46%) * Randomization was balanced between treatment groups, except in Study 2 in which twice as many patients were randomized to each of the active treatment groups compared to placebo.

In 76% of febuxostat 80 mg patients, reduction in serum uric acid levels to less than 6 mg/dL was noted by the Week 2 visit. Average serum uric acid levels were maintained at 6 mg/dL or below throughout treatment in 83% of these patients. In all treatment groups, fewer patients with higher baseline serum urate levels (≥10 mg/dL) and/o… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility Two-year carcinogenicity studies were conducted in F344 rats and B6C3F1 mice. Increased transitional cell papilloma and carcinoma of the urinary bladder was observed at 24 mg/kg (25 times the MRHD on an AUC basis and 18.75 mg/kg (12.5 times the MRHD on an AUC basis) in male rats and female mice, respectively. The urinary bladder neoplasms were secondary to calculus formation in the kidney and urinary bladder.

Febuxostat showed a positive clastogenic response in a chromosomal aberration assay in a Chinese hamster lung fibroblast cell line with and without metabolic activation in vitro . Febuxostat was negative in the following genotoxicity assays: the in vitro Ames assay, in vitro chromosomal aberration assay in human peripheral lymphocytes, the L5178Y mouse lymphoma cell line assay, the in vivo mouse micronucleus assay, and the rat unscheduled DNA synthesis assay. Fertility and reproductive performance were unaffected in male or female rats that received febuxostat at oral doses up to 48 mg/kg/day (approximately 31 and 40 times the MRHD on an AUC basis in males and females respectively).

13.2Animal Toxicology A 12-month toxicity study in beagle dogs showed deposition of xanthine crystals and calculi in kidneys at 15 mg/kg (approximately 4 times the MRHD on an AUC basis). A similar effect of calculus formation was noted in rats in a 6-month study due to deposition of xanthine crystals at 48 mg/kg (approximately 31 and 40 times the MRHD on an AUC basis in males and females respectively).