1.1 Type 1 Gaucher Disease

YARGESA is indicated as monotherapy for the treatment of adult patients with mild to moderate type 1 Gaucher disease for whom enzyme replacement therapy is not a therapeutic option (e.g. due to allergy, hypersensitivity, or poor venous access). 

2.1 Instructions for Administration

Therapy should be directed by physicians who are knowledgeable in the management of Gaucher disease.
The recommended dose for the treatment of adult patients with type 1 Gaucher disease is one 100 mg capsule administered orally three times a day at regular intervals. If a dose is missed, the next YARGESA capsule should be taken at the next scheduled time.
It may be necessary to reduce the dose to one 100 mg capsule once or twice a day in some patients due to adverse reactions, such as tremor or diarrhea.

2.2 Patients with Renal Insufficiency

In patients with mild renal impairment (adjusted creatinine clearance 50-70 mL/min/1.73 m2), initiate YARGESA treatment at a dose of 100 mg twice per day. In patients with moderate renal impairment (adjusted creatinine clearance of 30-50 mL/min/1.73 m2), initiate YARGESA treatment at a dose of one 100 mg capsule per day. YARGESA is not recommended for use in patients with severe renal impairment (creatinine clearance <30 mL/min/1.73 m2) [see Use in Specific Populations (8.6)].

5.1 Peripheral Neuropathy

In clinical trials, cases of peripheral neuropathy have been reported in 3% of Gaucher‘s patients treated with miglustat capsules. All patients receiving miglustat capsules treatment should undergo baseline and repeat neurological evaluations at approximately 6-month intervals. Patients who develop symptoms of peripheral neuropathy such as pain, weakness, numbness and tingling should have a careful re-assessment of the risk/benefit of miglustat therapy, and cessation of treatment may be considered.

5.2 Tremor

Approximately 30% of patients have reported tremor or exacerbation of existing tremor on treatment. These tremors were described as an exaggerated physiological tremor of the hands. Tremor usually began within the first month of therapy and in many cases resolved between 1 to 3 months during treatment. Reduce dose to ameliorate tremor or discontinue treatment if tremor does not resolve within days of dose reduction.

5.3 Diarrhea and Weight Loss

Diarrhea and weight loss were common in clinical studies of patients treated with miglustat capsules, occurring in approximately 85% and up to 65% of treated patients, respectively. Diarrhea appears to be the result of the inhibitory activity of miglustat on intestinal disaccharidases such as sucrase-isomaltase in the gastrointestinal tract leading to reduced absorption of dietary disaccharides in the small intestine, with a resultant osmotic diarrhea. It is unclear if weight loss results from the diarrhea and associated gastrointestinal complaints, a decrease in food intake, or a combination of these or other factors. The incidence of weight loss was most evident in the first 12 months of treatment. Diarrhea decreased over time with continued miglustat treatment, and may respond to individualized diet modification (e.g., reduction of sucrose, lactose and other carbohydrate intake), to taking miglustat capsules between meals, and/or to anti-diarrheal medications, most commonly loperamide. Patients may be instructed to avoid high carbohydrate content foods during treatment with miglustat capsules if they present with diarrhea.
Patients with persistent gastrointestinal events that continue during treatment with miglustat capsules, and who do not respond to usual interventions (e.g. diet modification), should be evaluated to determine whether significant underlying gastrointestinal disease is present. The safety of treatment with miglustat capsules has not been evaluated in patients with significant gastrointestinal disease, such as inflammatory bowel disease, and continued treatment of these patients with miglustat capsules should occur only after consideration of the risks and benefits of continued treatment.

5.4 Reductions in Platelet Count

In clinical trials evaluating the use of miglustat capsules for treatment of indications other than type 1 Gaucher disease, mild reductions in platelet counts without association with bleeding were observed in some patients; approximately 40% of patients in this trial had low platelet counts (defined as below 150 × 109/L) before starting treatment with miglustat capsules. Monitoring of platelet counts is recommended in patients with type 1 Gaucher
disease. Mild reductions in platelet counts without association with bleeding were observed in patients with type 1 Gaucher disease who were switched from enzyme replacement therapy (ERT) to miglustat capsules.

6.1 Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
The data described below reflect exposure of 80 patients with type 1 Gaucher disease in two open-label, uncontrolled, monotherapy trials, one open-label, active-controlled trial, and two extensions, who received miglustat capsules at doses ranging from 50 mg to 200 mg three times daily. Patients were aged 18 to 69 years at first treatment. The population was evenly distributed by gender.
The most common serious adverse reaction reported with miglustat capsules treatment in clinical trials was peripheral neuropathy [see Warnings and Precautions (5.1)].
The most commonly reported adverse reactions in patients treated with miglustat capsules (occurring in ≥ to 5%) that were considered related to miglustat capsules are shown in Tables 1 and 2. [see Warnings and Precautions (5.2, 5.3)].
The most common adverse reactions requiring intervention were diarrhea and tremor. [see Warnings and Precautions (5.2, 5.3)].
In two open-label, uncontrolled monotherapy trials, adult type 1 Gaucher disease patients were treated with miglustat capsules at a starting dose of 100 mg three times daily (dose range 100 to 200 mg three times daily) for up to 12 months in 28 patients [Study 1], or at a dose of 50 mg three times daily for up to 6 months in 18 patients [Study 2]. Table 1 below lists adverse reactions that occurred during the trials in ≥ to 5% of patients.

 In an open-label, active-controlled study, 36 adult type 1 Gaucher disease patients were treated with miglustat capsules, imiglucerase, or miglustat capsules plus imiglucerase [Study 3] for up to 12 months. Table 2 lists adverse reactions that occurred during the trial in greater than or equal to 5% of patients.

8.1 Pregnancy

Risk Summary
Based on findings from animal reproduction studies, miglustat capsules may cause fetal harm when administered to a pregnant woman. Available data from postmarketing case reports with miglustat capsules use in pregnancy are insufficient to assess a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. There are risks associated with symptomatic Type I Gaucher disease in pregnancy, including hepatosplenomegaly and thrombocytopenia (see Clinical Considerations). Advise pregnant women of the potential risks to the fetus.

In animal reproduction studies, miglustat was maternally toxic in rabbits at exposures near the expected human therapeutic dose and caused embryo-fetal toxicities in rats at doses twice the recommended human dose. No adverse developmental outcomes were observed with administration of miglustat to pregnant rats at dose levels 6 times the recommended human dose. (see Data).
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.

Clinical Considerations
Disease-associated maternal and embryo-fetal risk
Pregnancy may exacerbate existing Type 1 Gaucher disease symptoms or result in new disease manifestations. Type 1 Gaucher disease manifestations may lead to adverse pregnancy outcomes including, hepatosplenomegaly which can interfere with the normal growth of a pregnancy and thrombocytopenia which can lead to increased bleeding and possible hemorrhage.

Data

Animal Data
In female rats given miglustat by oral gavage at doses of 20, 60, 180 mg/kg/day beginning 14 days before mating and continuing through gestation day 17 (organogenesis), increased post implantation loss, decreased embryo-fetal survival and decreased fetal and pup weights were observed at doses greater than or equal to 60 mg/kg/day (greater than or equal to 2 times the human therapeutic dose on a mg/m2 basis). Miglustat was also administered to pregnant rats by oral gavage at doses of 20, 60, 180 mg/kg/day from gestation day 6 through lactation (postpartum day 20). Delayed and prolonged parturition with decreased live births were observed at doses greater than or equal to 60 mg/kg/day (greater than or equal
to 2 times the human therapeutic dose on a mg/m2 basis).
In pregnant rabbits given miglustat by oral gavage at doses of 15, 30, 45 mg/kg/day during gestation days 6-18 (organogenesis), maternal toxicity, including maternal deaths (all doses), reduced food consumption (30 and 45 mg/kg/day), and decreased body weight gain (15 and 30 mg/kg/day), was observed. The 15 mg/kg/day dose level was 0.97 times the human therapeutic dose on a mg/m2 basis.
A pre- and postnatal development study in rats, miglustat was administered by oral gavage at doses of 20, 60, 180 mg/kg/day from gestation day 6 through day 20 of lactation, decreased live births were observed in dams, as well as decreased body weight gain in the offspring at doses greater than or equal to 60 mg/kg/day (greater than or equal to 2 times the human therapeutic dose on a mg/m2 basis). There was no effect on behavioral and learning assessments, sexual maturation or reproductive performance of the offspring at doses up to 180 mg/kg/day (about 6 times the human therapeutic dose on a mg/m2 basis).

8.2 Lactation

Risk Summary
There are no available data on the presence of miglustat in either human or animal milk, the effects on the breastfed infant, or the effects on milk production. Based on the physical properties of miglustat, miglustat capsules is likely to be present in breast milk. Because of the potential for serious adverse reactions in breastfed infants, advise women that breastfeeding is not recommended.

8.3 Females and Males of Reproductive Potential

Infertility
Findings from a small clinical study in seven healthy adult males who received miglustat for six weeks did not indicate effects on male fertility. Studies in male rats have shown that miglustat decreased fertility but findings were reversible. Studies in female rats have shown increased post-implantation loss and decreased embryo-fetal survival [see Use in Specific Populations (8.1),Nonclinical Toxicology (13.1)].

8.4 Pediatric Use

The safety and effectiveness of miglustat capsules in pediatric patients have not been established.
In a combined clinical trial safety data set of 45 patients less than 18 years of age exposed to miglustat capsules in indications other than type 1 Gaucher disease, the median weight and height percentiles adjusted for age and gender decreased during the first year of treatment but then stabilized. The mean length of exposure in these studies ranged from 2 to 2.6 years; some pediatric patients were exposed for up to 4 years. However, the effect of miglustat capsules on long-term gain in weight and height in pediatric patients is unclear.

8.5 Geriatric Use

Clinical studies of miglustat capsules did not include sufficient numbers of patients aged 65 and over to determine whether they respond differently than younger patients. Other reported clinical experience has not identified differences in responses between elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, and cardiac function and of concomitant disease or other drug therapy.

8.6 Renal Impairment

Miglustat is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in patients with impaired renal function [see Clinical Pharmacology (12.3)].
In patients with mild renal impairment (adjusted creatinine clearance 50-70 mL/min/1.73 m2), miglustat capsules administration should commence at a dose of 100 mg twice per day.
In patients with moderate renal impairment (adjusted creatinine clearance of 30-50 mL/min/1.73 m2), miglustat capsules administration should commence at a dose of 100 mg once a day.
Use of miglustat capsules in patients with severe renal impairment (creatinine clearance less than 30 mL/min/1.73 m2) is not recommended.
Since elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function. The impact of hemodialysis on the disposition of miglustat capsules has not been investigated.

12.1 Mechanism of Action

Type 1 Gaucher disease is caused by a functional deficiency of glucocerebrosidase, the enzyme that mediates the degradation of the glycosphingolipid glucosylceramide.
Miglustat functions as a competitive and reversible inhibitor of the enzyme glucosylceramide synthase, the initial enzyme in a series of reactions which results in the synthesis of most glycosphingolipids.
Miglustat capsules helps reduce the rate of glycosphingolipid biosynthesis so that the amount of glycosphingolipid substrate is reduced to a level which allows the residual activity of the deficient glucocerebrosidase enzyme to be more effective (substrate reduction therapy). In vitro and in vivo studies have shown that miglustat can reduce the synthesis of glucosylceramide-based glycosphingolipids.

12.3 Pharmacokinetics

Absorption:
After a 100 mg oral dose, the time to maximum observed plasma concentration of miglustat (tmax) ranged from 2 to 2.5 hours in Gaucher patients. Plasma concentrations show a biexponential decline, characterized by a short distribution phase and a longer elimination phase. The effective half-life of miglustat is approximately 6 to 7 hours, which predicts that steady-state will be achieved by 1.5 to 2 days following the start of three times daily dosing. Miglustat, dosed at 50 and 100 mg three times daily in Gaucher patients, exhibits dose-proportional pharmacokinetics. The pharmacokinetics of miglustat were not altered after repeated dosing three times daily for up to 12 months.
In healthy subjects, co-administration of miglustat capsules with food results in a decrease in the rate of absorption of miglustat (maximum plasma concentration [Cmax] was decreased by 36% and tmax delayed 2 h) but had no statistically significant effect on the extent of absorption of miglustat (area-under-the-plasma-concentration time curve [AUC] was decreased by 14%). The mean oral bioavailability of a 100-mg miglustat capsule is about 97% relative to an oral solution administered under fasting conditions. The pharmacokinetics of miglustat were similar between adult type 1 Gaucher disease patients and healthy subjects after a single dose administration of miglustat 100 mg.

Distribution:
Miglustat does not bind to plasma proteins. Mean apparent volume of distribution of miglustat is 83-105 liters in Gaucher patients. At steady state, the concentration of miglustat in cerebrospinal fluid of six non-Gaucher patients was 31.4-67.2% of that in plasma, indicating that miglustat crosses the blood brain barrier.

Metabolism and Excretion:
The major route of excretion of miglustat is via kidney. Following administration of a single dose of 100 mg 14C-miglustat to healthy volunteers, 83% of the radioactivity was recovered in urine and 12% in feces. In healthy subjects, 67% of the administered dose was excreted unchanged in urine over 72 hours. The most abundant metabolite in urine was miglustat glucuronide accounting for 5% of the dose. The terminal half-life of radioactivity in plasma was 150 hours, suggesting the presence of one or more metabolites with a prolonged half-life. The metabolite accounting for this observation has not been identified but may accumulate and reach concentrations exceeding those of miglustat at steady state.

Specific Populations
Gender: There was no statistically significant gender difference in miglustat pharmacokinetics, based on pooled data analysis.

Race: Ethnic differences in miglustat pharmacokinetics have not been evaluated in Gaucher patients. However, apparent oral clearance of miglustat in patients of Ashkenazi Jewish descent was not statistically different to that in others (1 Asian and 15 Caucasians), based on a cross-study analysis.

Hepatic Impairment: No studies have been performed to assess the pharmacokinetics of miglustat in patients with hepatic impairment.

Renal Impairment: Limited data in non-Gaucher patients with impaired renal function indicate that the apparent oral clearance (CL/F) of miglustat decreases with decreasing renal function. While the number of subjects with mild and moderate renal impairment was very small, the data suggest an approximate decrease in the apparent oral clearance of 40% and 60% respectively, in mild and moderate renal impairment, justifying the need to decrease the dosing of miglustat in such patients dependent upon creatinine clearance levels [see Dosage and Administration (2.2)].
Data in severe renal impairment are limited to two patients with creatinine clearances in the range 18-29 mL/min and cannot be extrapolated below this range. These data suggest a decrease in CL/F by at least 70% in patients with severe renal impairment [see Dosage and Administration (2.2) and Use in Specific Populations (8.6)].

Drug Interaction Studies
Miglustat does not inhibit the metabolism of various substrates of cytochrome P450 enzymes including, CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4 and CYP4A11 in vitro; consequently significant interactions via inhibition of these enzymes are unlikely with drugs that are substrates of cytochrome P450 enzymes.

Drug interaction between miglustat capsules (miglustat 100 mg orally three times daily) and imiglucerase 7.5 or 15 U/kg/day was assessed in imiglucerase-stabilized patients after one month of co-administration. There was no significant effect of imiglucerase on the pharmacokinetics of miglustat, with the co-administration of imiglucerase and miglustat resulting in a 22% reduction in Cmax and a 14% reduction in the AUC for miglustat. While miglustat capsules appeared to increase the clearance of imiglucerase by 70%, these results are not conclusive because of the small number of subjects studied and because patients took variable doses of imiglucerase [see Drug Interactions (7)]. Concomitant therapy with loperamide during clinical trials did not appear to significantly alter the pharmacokinetics
of miglustat.

13.1 Carcinogenesis, Mutagenesis, Impairment Of Fertility

Carcinogenesis:
Two-year carcinogenicity studies have been conducted with miglustat in CD-1 mice at oral doses up to 500 mg/kg/day and in Sprague Dawley rats at oral doses up to 180 mg/kg/day. Oral administration of miglustat for 104 weeks produced mucinous adenocarcinomas of the large intestine at 210, 420 and 500 mg/kg/day (about 3, 6 and 7 times the recommended human dose, respectively, based on the body surface area) in male mice and at 420 and 500 mg/kg/day (about 6 and 7 times the recommended human dose, based on the body surface area) in female mice. The adenocarcinomas were considered rare in CD-1 mice and occurred in the presence of inflammatory and hyperplastic lesions in the large intestine of both males and females. In rats, oral administration of miglustat for 100 weeks produced increased incidences of interstitial cell adenomas of the testis at 30, 60 and 180 mg/kg/day (about 1, 2 and 5 times the recommended human dose, respectively, based on the body surface area).

Mutagenesis:
Miglustat was not mutagenic or clastogenic in a battery of in vitro and in vivo assays including the bacterial reverse mutation (Ames), chromosomal aberration (in human lymphocytes), gene mutation in mammalian cells (Chinese hamster ovary), and mouse micronucleus assays.

Impairment of Fertility:
Miglustat was administered by oral gavage to male rats at doses of 20, 60, 180 mg/kg/day beginning at least 14 days prior to mating and continuing through mating. Effects on sperm parameters (concentration, motility and morphology) resulting in decreased fertility were observed at all dose levels (the lowest dose level was 0.65 times the human therapeutic dose on a mg/m2 basis). Reversibility was demonstrated following 6 weeks of drug withdrawal. Findings of, seminiferous tubule degeneration and atrophy were observed in the testes in rat repeat-dose toxicity studies.

Miglustat was administered by oral gavage to female rats at doses of 20, 60, 180 mg/kg/day beginning 14 days before mating and continuing through gestation day 17. There were no effects on mating performance or fertility in female rats at doses up to 180 mg/kg/day. However, increased post implantation loss and decreased embryo-fetal survival were observed at doses greater than or equal to 60 mg/kg/day (≥ 2 times the human therapeutic dose on a mg/m2 basis).

13.2 Animal Toxicology and/or Pharmacology

Histopathology findings in the absence of clinical signs in the central nervous system of the monkey (brain, spine) that included vascular mineralization, in addition to mineralization and necrosis of white matter were observed at greater than 750 mg/kg/day (4 times the human therapeutic systemic exposure based on area-under-the-plasma-concentration curve [AUC] comparisons) in a 52-week oral toxicity study using  doses of 750 and 2000 mg/kg/d. Vacuolization of white matter was observed in rats dosed orally by gavage at greater than or equal to 180 mg/kg/d (6 times the human therapeutic exposure based on surface area comparisons, mg/m2) in a 4-week study using doses of 180, 840, and 4200 mg/kg/d.
Vacuolization can sometimes occur as an artifact of tissue processing. Findings in dogs included tremor and absent corneal reflexes at 105 mg/kg/day (10 times the human therapeutic systemic exposure, based on body surface area comparisons, mg/m2) after a 4-week oral gavage toxicity study using doses of 35, 70, 105, and 140 mg/kg/d. Ataxia, diminished/absent pupillary, palpebral, or patellar reflexes were observed in a dog at greater than or equal to 495 mg/kg/day (50 times the human therapeutic systemic exposure based on body surface area comparisons, mg/m2), in a 2-week oral gavage toxicity study using doses of 85, 165, 495, and 825 mg/kg/d.
Cataracts were observed in rats at greater than or equal to 180 mg/kg/day (4 times the human therapeutic systemic exposure, based on AUC) in a 52-week oral gavage toxicity study using doses of 180, 420, 840, and 1680 mg/kg/d.
Gastrointestinal necrosis, inflammation, and hemorrhage were observed in dogs at greater than or equal to 85 mg/kg/day (9 times the human therapeutic systemic exposure based on body surface area comparisons, mg/m2) after a 2-week oral (capsule) toxicity study using doses of 85, 165, 495, and 825 mg/kg/d. Similar GI toxicity occurred in rats at 1200 mg/kg/day (7 times the human therapeutic systemic exposure, based on AUC) in a 26-week oral gavage toxicity study using doses of 300, 600, and 1200 mg/kg/d. In monkeys, similar GI toxicity occurred at greater than or equal to 750 mg/kg/day (6 times the human therapeutic systemic exposure based on AUC) following a 52-week oral gavage toxicity study using doses of 750 and 2000 mg/kg/d.