Physiogel Cream

Glycerol:

• Dosage and administration
• Dosage forms and strengths
• Contraindications
• Warnings and precautions
• Adverse reactions
• Drug interactions
• Use in specific populations
• Overdosage
• Description
• Clinical pharmacology
• Nonclinical toxicology
• Clinical studies
• How supplied/storage and handling
• Patient counseling information
• Physiogel Cream (Glycerol) reviews

Physiogel Cream (Glycerol) is indicated for use as a nitrogen-binding agent for chronic management of patients 2 months of age and older with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. Physiogel Cream (Glycerol) must be used with dietary protein restriction and, in some cases, dietary supplements (e.g., essential amino acids, arginine, citrulline, protein-free calorie supplements).

Limitations of Use:

• Physiogel Cream (Glycerol) is not indicated for the treatment of acute hyperammonemia in patients with UCDs because more rapidly acting interventions are essential to reduce plasma ammonia levels.
• The safety and efficacy of Physiogel Cream (Glycerol) for the treatment of N-acetylglutamate synthase (NAGS) deficiency has not been established.

Physiogel Cream (Glycerol) is a nitrogen-binding agent indicated for chronic management of patients 2 months of age and older with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. Physiogel Cream (Glycerol) must be used with dietary protein restriction and, in some cases, dietary supplements. (1)

Limitations of Use:

• Physiogel Cream (Glycerol) is not indicated for treatment of acute hyperammonemia in patients with UCDs. (1)
• Safety and efficacy for treatment of N-acetylglutamate synthase (NAGS) deficiency has not been established. (1)

2 DOSAGE AND ADMINISTRATION

• Physiogel Cream should be prescribed by a physician experienced in management of UCDs. For administration and preparation, see full prescribing information. (2.1, 2.6)

Switching From Sodium Phenylbutyrate Tablets or Powder to Physiogel Cream (Glycerol):

• Patients should receive the dosage of Physiogel Cream (Glycerol) that contains the same amount of phenylbutyric acid, see full prescribing information for conversion. (2.2)

Initial Dosage in Phenylbutyrate-Naïve Patients (2.3):

• Recommended dosage range is 4.5 to 11.2 mL/m²/day (5 to 12.4 g/m²/day).
• For patients with some residual enzyme activity not adequately controlled with dietary restriction, the recommended starting dose is 4.5 mL/m²/day.
• Take into account patient's estimated urea synthetic capacity, dietary protein intake, and diet adherence.

Dosage Adjustment and Monitoring:

• Follow plasma ammonia levels to determine the need for dosage titration. (2.4)

Dosage Modifications in Patients with Hepatic Impairment:

• Start dosage at lower end of range. (2.5, 8.6)

2.1 Important Administration Instructions

Physiogel Cream (Glycerol) should be prescribed by a physician experienced in the management of UCDs.

• Instruct patients to take Physiogel Cream (Glycerol) with food or formula and to administer directly into the mouth via oral syringe or dosing cup.
• For patients who cannot swallow, see the instructions on administration of Physiogel Cream (Glycerol) by nasogastric tube or gastrostomy tube .
• For patients who require a volume of less than 1 mL per dose via nasogastric or gastrostomy tube, the delivered dose may be less than anticipated. Closely monitor these patients using ammonia levels .
• The recommended dosages for patients switching from sodium phenylbutyrate to Physiogel Cream (Glycerol) and patients naïve to phenylbutyric acid are different . For both subpopulations:
  • Patients 2 years of age and older: Give Physiogel Cream (Glycerol) in 3 equally divided dosages, each rounded up to the nearest 0.5 mL
  • Patients 2 months of age to less than 2 years: Give Physiogel Cream (Glycerol) in 3 or more equally divided dosages, each rounded up to the nearest 0.1 mL.
  • The maximum total daily dosage is 17.5 mL (19 g).
  • Physiogel Cream (Glycerol) must be used with dietary protein restriction and, in some cases, dietary supplements (e.g., essential amino acids, arginine, citrulline, protein-free calorie supplements).

2.2 Switching From Sodium Phenylbutyrate to Physiogel Cream

Patients switching from sodium phenylbutyrate to Physiogel Cream (Glycerol) should receive the dosage of Physiogel Cream (Glycerol) that contains the same amount of phenylbutyric acid. The conversion is as follows:

Total daily dosage of Physiogel Cream (Glycerol) (mL) = total daily dosage of sodium phenylbutyrate tablets (g) × 0.86

Total daily dosage of Physiogel Cream (Glycerol) (mL) = total daily dosage of sodium phenylbutyrate powder (g) × 0.81

2.3 Initial Dosage in Phenylbutyrate-Naïve Patients

The recommended dosage range, based upon body surface area, in patients naïve to phenylbutyrate is 4.5 to 11.2 mL/m²/day (5 to 12.4 g/m²/day). For patients with some residual enzyme activity who are not adequately controlled with protein restriction, the recommended starting dosage is 4.5 mL/m²/day.

In determining the starting dosage of Physiogel Cream (Glycerol) in treatment-naïve patients, consider the patient's residual urea synthetic capacity, dietary protein requirements, and diet adherence. Dietary protein is approximately 16% nitrogen by weight. Given that approximately 47% of dietary nitrogen is excreted as waste and approximately 70% of an administered PBA dose will be converted to urinary phenylacetylglutamine (U-PAGN), an initial estimated Physiogel Cream (Glycerol) dose for a 24-hour period is 0.6 mL Physiogel Cream (Glycerol) per gram of dietary protein ingested per 24-hour period. The total daily dosage should not exceed 17.5 mL.

2.4 Dosage Adjustment and Monitoring

During treatment with Physiogel Cream (Glycerol), patients should be followed clinically and with plasma ammonia levels to determine the need for dosage titration. Closely monitor ammonia levels after changing the dosage of Physiogel Cream (Glycerol).

Normal Ammonia Levels

If patients experience symptoms of vomiting, nausea, headache, somnolence or confusion in the absence of high ammonia levels or other intercurrent illnesses, reduce the Physiogel Cream (Glycerol) dosage and monitor patients clinically. If available, obtain measurements of plasma phenylacetate (PAA) concentrations and the ratio of plasma PAA to PAGN to guide dosing. A high PAA to PAGN ratio may indicate the saturation of the conjugation reaction to form PAGN. The PAA to PAGN ratio has been observed to be generally less than 1 in patients with UCDs without significant PAA accumulation .

Elevated Ammonia Levels

When plasma ammonia is elevated, increase the Physiogel Cream (Glycerol) dosage to reduce the fasting ammonia level to less than half the upper limit of normal (ULN) in patients 6 years and older. In infants and pediatric patients (generally below 6 years of age), where obtaining fasting ammonia is problematic due to frequent feedings, adjust the dosage to keep the first ammonia of the morning below the ULN.

Urinary Phenylacetylglutamine: If available, U-PAGN measurements may be used to help guide Physiogel Cream (Glycerol) dosage adjustment. Each gram of U-PAGN excreted over 24 hours covers waste nitrogen generated from 1.4 grams of dietary protein. If U-PAGN excretion is insufficient to cover daily dietary protein intake and the fasting ammonia is greater than half the ULN, the Physiogel Cream (Glycerol) dosage should be adjusted upward. The amount of dosage adjustment should factor in the amount of dietary protein that has not been covered, as indicated by the 24-hour U-PAGN level and the estimated Physiogel Cream (Glycerol) dose needed per gram of dietary protein ingested and the maximum total daily dosage (i.e., 17.5 mL).

Consider a patient's use of concomitant medications, such as probenecid, when making dosage adjustment decisions based on U-PAGN. Probenecid may result in a decrease of the urinary excretion of PAGN .

Plasma Phenylacetate and Phenylacetylglutamine: If available, the ratio of PAA to PAGN in plasma may provide additional information to assist in dosage adjustment decisions. In patients with a high PAA to PAGN ratio, a further increase in Physiogel Cream (Glycerol) dosage may not increase PAGN formation, even if plasma PAA concentrations are increased, due to saturation of the conjugation reaction .

2.5 Dosage Modifications in Patients with Hepatic Impairment

For patients with moderate to severe hepatic impairment, the recommended starting dosage is at the lower end of the recommended dosing range and kept at the lowest dose necessary to control the patient's ammonia levels .

2.6 Preparation for Nasogastric Tube or Gastrostomy Tube Administration

It is recommended that all patients who can swallow take Physiogel Cream (Glycerol) orally, even those with nasogastric and/or gastrostomy tubes. However, for patients who cannot swallow, a nasogastric tube or gastrostomy tube may be used to administer Physiogel Cream (Glycerol) as follows:

• Utilize an oral syringe to withdraw the prescribed dosage of Physiogel Cream (Glycerol) from the bottle.
• Place the tip of the syringe into the nasogastric/gastrostomy tube.
• Utilizing the plunger of the syringe, administer Physiogel Cream (Glycerol) into the tube.
• Flush once with 10 mL of water or formula and allow the flush to drain.
• If needed, flush a second time with an additional 10 mL of water or formula to clear the tube.

For patients who require a volume of less than 1 mL per dose via nasogastric or gastrostomy tube, the delivered dosage may be less than anticipated due to adherence of Physiogel Cream (Glycerol) to the plastic tubing. Therefore, these patients should be closely monitored using ammonia levels following initiation of Physiogel Cream (Glycerol) dosing or dosage adjustments.

3 DOSAGE FORMS AND STRENGTHS

Oral liquid: colorless to pale yellow, 1.1 g/mL of Physiogel Cream (Glycerol) phenylbutyrate (delivers 1.02 g/mL of phenylbutyrate).

Oral liquid: 1.1 g/mL. (3)

4 CONTRAINDICATIONS

Physiogel Cream (Glycerol) is contraindicated in patients

• Less than 2 months of age. Pediatric patients less than 2 months of age may have immature pancreatic exocrine function, which could impair hydrolysis of Physiogel Cream (Glycerol), leading to impaired absorption of phenylbutyrate and hyperammonemia .
• With known hypersensitivity to phenylbutyrate. Signs of hypersensitivity include wheezing, dyspnea, coughing, hypotension, flushing, nausea, and rash.

• Patients less than 2 months of age. (4)
• Known hypersensitivity to phenylbutyrate. (4)

5 WARNINGS AND PRECAUTIONS

• Neurotoxicity: Phenylacetate, the active moiety of Physiogel Cream (Glycerol), may be toxic; reduce dosage for symptoms of neurotoxicity. (5.1)
• Reduced Phenylbutyrate Absorption in Pancreatic Insufficiency or Intestinal Malabsorption: Monitor ammonia levels closely. (5.2)

5.1 Neurotoxicity

The major metabolite of Physiogel Cream (Glycerol), PAA, is associated with neurotoxicity. Signs and symptoms of PAA neurotoxicity, including somnolence, fatigue, lightheadedness, headache, dysgeusia, hypoacusis, disorientation, impaired memory, and exacerbation of preexisting neuropathy, were observed at plasma PAA concentrations of 500 micrograms/mL in a study of adult cancer patients who were administered PAA intravenously. In this study, adverse reactions were reversible.

In healthy subjects, after administration of 4 mL and 6 mL Physiogel Cream (Glycerol) 3 times daily for 3 days, a dose-dependent increase in all-grade nervous system adverse reactions was observed, even at exposure levels of PAA less than 100 micrograms/mL.

In clinical trials in patients with UCDs who had been on sodium phenylbutyrate prior to administration of Physiogel Cream (Glycerol), peak PAA concentrations after dosing with Physiogel Cream (Glycerol) ranged from 1.6 to 178 micrograms/mL (mean: 39 micrograms/mL) in adult patients, from 1 to 410 micrograms/mL (mean: 70 micrograms/mL; median: 50 micrograms/mL) in pediatric patients ages 2 years and older, and from 1 to 1215 micrograms/mL (mean: 142 micrograms/mL; median: 35 micrograms/mL) in pediatric patients ages 2 months to less than 2 years. Some patients with UCDs experienced headache, fatigue, symptoms of peripheral neuropathy, seizures, tremor and/or dizziness. No correlation between PAA levels and neurotoxicity symptoms was identified but PAA levels were generally not measured at the time of neurotoxicity symptoms.

If symptoms of vomiting, nausea, headache, somnolence or confusion, are present in the absence of high ammonia or other intercurrent illnesses, reduce the Physiogel Cream (Glycerol) dosage .

5.2 Reduced Phenylbutyrate Absorption in Pancreatic Insufficiency or Intestinal Malabsorption

Exocrine pancreatic enzymes hydrolyze Physiogel Cream (Glycerol) in the small intestine, separating the active moiety, phenylbutyrate, from Physiogel Cream (Glycerol). This process allows phenylbutyrate to be absorbed into the circulation. Low or absent pancreatic enzymes or intestinal disease resulting in fat malabsorption may result in reduced or absent digestion of Physiogel Cream (Glycerol) and/or absorption of phenylbutyrate and reduced control of plasma ammonia. Monitor ammonia levels closely in patients with pancreatic insufficiency or intestinal malabsorption.

6 ADVERSE REACTIONS

Most common adverse reactions in adults are: diarrhea, flatulence, and headache. (6.1)

To report SUSPECTED ADVERSE REACTIONS, contact Horizon Therapeutics at 1-855-823-7878 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

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 clinical practice.

Assessment of adverse reactions was based on exposure of 45 adult patients (31 female and 14 male) with UCD subtype deficiencies of ornithine transcarbamylase (OTC, n=40), carbamyl phosphate synthetase (CPS, n=2), and argininosuccinate synthetase (ASS, n=1) in a randomized, double-blind, active-controlled (RAVICTI vs sodium phenylbutyrate), crossover, 4-week study (Study 1) that enrolled patients 18 years of age and older . One of the 45 patients received only sodium phenylbutyrate prior to withdrawing on day 1 of the study due to an adverse reaction.

The most common adverse reactions (occurring in at least 10% of patients) reported during short-term treatment with Physiogel Cream (Glycerol) were diarrhea, flatulence, and headache. Table 1 summarizes adverse reactions occurring in 2 or more patients treated with Physiogel Cream (Glycerol) or sodium phenylbutyrate (incidence of at least 4% in either treatment arm).

Other Adverse Reactions

Physiogel Cream (Glycerol) has been evaluated in 77 patients with UCDs (51 adult and 26 pediatric patients ages 2 years to 17 years) in 2 open-label long-term studies, in which 69 patients completed 12 months of treatment with Physiogel Cream (Glycerol) (median exposure = 51 weeks). During these studies there were no deaths.

Adverse reactions occurring in at least 10% of adult patients were nausea, vomiting, diarrhea, decreased appetite, dizziness, headache, and fatigue.

Adverse reactions occurring in at least 10% of pediatric patients ages 2 years to 17 years were upper abdominal pain, rash, nausea, vomiting, diarrhea, decreased appetite, and headache.

Physiogel Cream (Glycerol) has also been evaluated in 17 patients with UCDs ages 2 months to less than 2 years in 3 open-label studies. The median exposure was 6 months (range 0.2 to 18 months). Adverse reactions occurring in at least 10% of pediatric patients aged 2 months to less than 2 years were neutropenia, vomiting, diarrhea, pyrexia, hypophagia, cough, nasal congestion, rhinorrhea, rash and papule.

6.2 Postmarketing Experience

The following adverse reactions have been identified during postapproval use of Physiogel Cream (Glycerol). Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure:

• Abnormal body odor, including from skin, hair and urine
• Retching and gagging
• Dysgeusia or burning sensation in mouth

7 DRUG INTERACTIONS

• Corticosteroids, valproic acid, or haloperidol: May increase plasma ammonia level; monitor ammonia levels closely.
• Probenecid: May affect renal excretion of metabolites of Physiogel Cream (Glycerol), including phenylacetylglutamine (PAGN) and PAA. (7.2)
• CYP3A4 Substrates with narrow therapeutic index (e.g., alfentanil, quinidine, cyclosporine): Physiogel Cream (Glycerol) may decrease exposure; monitor for decreased efficacy of the narrow therapeutic index drug. (7.3)
• Midazolam: Decreased exposure; monitor for suboptimal effect of midazolam. (7.3)

7.1 Potential for Other Drugs to Affect Ammonia

Corticosteroids

Use of corticosteroids may cause the breakdown of body protein and increase plasma ammonia levels. Monitor ammonia levels closely when corticosteroids and Physiogel Cream (Glycerol) are used concomitantly.

Valproic Acid and Haloperidol

Hyperammonemia may be induced by haloperidol and by valproic acid. Monitor ammonia levels closely when use of valproic acid or haloperidol is necessary in patients with UCDs.

7.2 Potential for Other Drugs to Affect Physiogel Cream

Probenecid

Probenecid may inhibit the renal excretion of metabolites of Physiogel Cream (Glycerol) including PAGN and PAA.

7.3 Potential for Physiogel Cream to Affect Other Drugs

Drugs with narrow therapeutic index that are substrates of CYP3A4

Physiogel Cream (Glycerol) is a weak inducer of CYP3A4 in humans. Concomitant use of Physiogel Cream (Glycerol) may decrease the systemic exposure to drugs that are substrates of CYP3A4. Monitor for decreased efficacy of drugs with narrow therapeutic index (e.g., alfentanil, quinidine, cyclosporine) .

Midazolam

Concomitant use of Physiogel Cream (Glycerol) decreased the systemic exposure of midazolam. Monitor for suboptimal effect of midazolam in patients who are being treated with Physiogel Cream (Glycerol).

8 USE IN SPECIFIC POPULATIONS

Lactation: Breastfeeding is not recommended.

8.1 Pregnancy

Pregnancy Exposure Registry

There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to Physiogel Cream (Glycerol) during pregnancy. Healthcare providers are encouraged to report any prenatal exposure to Physiogel Cream (Glycerol) by calling the Pregnancy Registry at 1-855-823-2595 or visiting www.ucdregistry.com.

Risk Summary

Limited available data with Physiogel Cream (Glycerol) use in pregnant women are insufficient to inform a drug-associated risk of major birth defects and miscarriage. In an animal reproduction study, administration of oral Physiogel Cream (Glycerol) phenylbutyrate to pregnant rabbits during organogenesis at doses up to 2.7–times the dose of 6.87 mL/m²/day in adult patients resulted in maternal toxicity, but had no effects on embryo-fetal development. In addition, there were no adverse developmental effects with administration of oral Physiogel Cream (Glycerol) phenylbutyrate to pregnant rats during organogenesis at 1.9 times the dose of 6.87 mL/m²/day in adult patients; however, maternal toxicity, reduced fetal weights, and variations in skeletal development were observed in pregnant rats administered oral Physiogel Cream (Glycerol) phenylbutyrate during organogenesis at doses greater than or equal to 5.7 times the dose of 6.87 mL/m²/day in adult patients [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 to 4% and 15 to 20%, respectively.

Data

Animal Data

Oral administration of Physiogel Cream (Glycerol) phenylbutyrate during the period of organogenesis up to 350 mg/kg/day in rabbits produced maternal toxicity, but no effects on embryo-fetal development. The dose of 350 mg/kg/day in rabbits is approximately 2.7 times the dose of 6.87 mL/m²/day in adult patients, based on combined area under the plasma concentration-time curve [AUCs] for PBA and PAA. In rats, at an oral dose of 300 mg/kg/day of Physiogel Cream (Glycerol) phenylbutyrate (1.9 times the dose of 6.87 mL/m²/day in adult patients, based on combined AUCs for PBA and PAA) during the period of organogenesis, no effects on embryo-fetal development were observed. Doses of 650 mg/kg/day or greater produced maternal toxicity and adverse effects on embryo-fetal development including reduced fetal weights and cervical ribs at the 7th cervical vertebra. The dose of 650 mg/kg/day in rats is approximately 5.7 times the dose of 6.87 mL/m²/day in adult patients, based on combined AUCs for PBA and PAA. No developmental abnormalities, effects on growth, or effects on learning and memory were observed through maturation of offspring following oral administration in pregnant rats with up to 900 mg/kg/day of Physiogel Cream (Glycerol) phenylbutyrate (8.5 times the dose of 6.87 mL/m²/day in adult patients, based on combined AUCs for PBA and PAA) during organogenesis and lactation.

8.2 Lactation

Risk Summary

There are no data on the presence of Physiogel Cream in human milk, the effects on the breastfed infant, or the effects on milk production. Because of the potential for serious adverse reactions, including neurotoxicity and tumorigenicity in a breastfed infant, advise patients that breastfeeding is not recommended during treatment with Physiogel Cream (Glycerol).

8.4 Pediatric Use

Safety and efficacy of Physiogel Cream (Glycerol) have been established in pediatric patients 2 months of age and older with UCDs.

Physiogel Cream (Glycerol) is contraindicated in pediatric patients less than 2 months of age .

Patients 2 Years to Less Than 18 Years of Age

The safety and efficacy of Physiogel Cream (Glycerol) in patients 2 years to less than 18 years of age were established in 2 open-label, sodium phenylbutyrate to Physiogel Cream (Glycerol), fixed-sequence, switchover clinical studies .

Patients 2 Months to Less Than 2 Years of Age

The safety and efficacy of Physiogel Cream (Glycerol) in patients with UCDs, 2 months to less than 2 years of age were established in 3 open-label studies. Pharmacokinetics and pharmacodynamics (plasma ammonia), and safety were studied in 17 patients between 2 months and less than 2 years of age .

Patients Less Than 2 Months of Age

Physiogel Cream (Glycerol) is contraindicated in patients less than 2 months of age . Pediatric patients less than 2 months of age may have immature pancreatic exocrine function, which could impair hydrolysis of Physiogel Cream (Glycerol). Pancreatic lipases may be necessary for intestinal hydrolysis of Physiogel Cream (Glycerol), allowing release of phenylbutyrate and subsequent formation of PAA, the active moiety. It is not known whether pancreatic and extrapancreatic lipases are sufficient for hydrolysis of Physiogel Cream (Glycerol). If there is inadequate intestinal hydrolysis of Physiogel Cream (Glycerol), impaired absorption of phenylbutyrate and hyperammonemia could occur.

Juvenile Animal Toxicity Data

In a juvenile rat study with daily oral dosing performed on postpartum day 2 through mating and pregnancy after maturation, terminal body weight was dose-dependently reduced by up to 16% in males and 12% in females at 900 mg/kg/day or higher (3 times the dose of 6.87 mL/m²/day in adult patients, based on combined AUCs for PBA and PAA). Learning, memory, and motor activity endpoints were not affected. However, fertility (number of pregnant rats) was decreased by up to 25% at 650 mg/kg/day or higher (2.6 times the dose of 6.87 mL/m²/day in adult patients, based on combined AUCs for PBA and PAA).

8.5 Geriatric Use

Clinical studies of Physiogel Cream did not include sufficient numbers of subjects 65 years of age and older to determine whether they respond differently than younger subjects. Other reported clinical experience has not identified differences in responses between the 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, or cardiac function, and of concomitant disease or other drug therapy.

8.6 Renal Impairment

The efficacy and safety of Physiogel Cream (Glycerol) in patients with renal impairment are unknown. Monitor ammonia levels closely when starting patients with impaired renal function on Physiogel Cream (Glycerol).

8.7 Hepatic Impairment

No studies were conducted in patients with UCDs and hepatic impairment. Because conversion of PAA to PAGN occurs in the liver, patients with hepatic impairment may have reduced conversion capability and higher plasma PAA and PAA to PAGN ratio . Therefore, dosage for patients with moderate to severe hepatic impairment should be started at the lower end of the recommended dosing range and should be kept on the lowest dose necessary to control their ammonia levels .

10 OVERDOSAGE

While there is no experience with overdosage in human clinical trials, PAA, a toxic metabolite of Physiogel Cream (Glycerol), can accumulate in patients who receive an overdose .

If over-exposure occurs, call your Poison Control Center at 1-800-222-1222 for current information on the management of poisoning or overdosage.

11 DESCRIPTION

Physiogel Cream (Glycerol) (glycerol phenylbutyrate) is a clear, colorless to pale yellow oral liquid. It is insoluble in water and most organic solvents, and it is soluble in dimethylsulfoxide (DMSO) and greater than 65% acetonitrile.

Physiogel Cream (Glycerol) phenylbutyrate is a nitrogen-binding agent. It is a triglyceride containing 3 molecules of PBA linked to a Physiogel Cream (Glycerol) backbone, the chemical name of which is benzenebutanoic acid, 1', 1' ' –(1,2,3-propanetriyl) ester with a molecular weight of 530.67. It has a molecular formula of C₃₃H₃₈O₆. The structural formula is:

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

UCDs are inherited deficiencies of enzymes or transporters necessary for the synthesis of urea from ammonia. Absence of these enzymes or transporters results in the accumulation of toxic levels of ammonia in the blood and brain of affected patients. Physiogel Cream (Glycerol) is a triglyceride containing 3 molecules of phenylbutyrate (PBA). PAA, the major metabolite of PBA, is the active moiety of Physiogel Cream (Glycerol). PAA conjugates with glutamine (which contains 2 molecules of nitrogen) via acetylation in the liver and kidneys to form PAGN, which is excreted by the kidneys (Figure 1). On a molar basis, PAGN, like urea, contains 2 moles of nitrogen and provides an alternate vehicle for waste nitrogen excretion.

Figure 1: RAVICTI Mechanism of Action

12.2 Pharmacodynamics

Pharmacological Effects

In clinical studies, total 24-hour area under the plasma concentration-time curve (AUC) of ammonia concentration was comparable at steady state during the switchover period between Physiogel Cream (Glycerol) and sodium phenylbutyrate .

Cardiac Electrophysiology

The effect of multiple doses of Physiogel Cream (Glycerol) 13.2 g/day and 19.8 g/day (approximately 69% and 104% of the maximum recommended daily dosage) on QTc interval was evaluated in a randomized, placebo- and active-controlled (moxifloxacin 400 mg), four-treatment-arm, crossover study in 57 healthy subjects. The upper bound of the one-sided 95% CI for the largest placebo-adjusted, baseline-corrected QTc, based on individual correction method (QTcI) for Physiogel Cream (Glycerol), was below 10 ms. However, assay sensitivity was not established in this study because the moxifloxacin time-profile was not consistent with expectation. Therefore, an increase in mean QTc interval of 10 ms cannot be ruled out.

12.3 Pharmacokinetics

Absorption

Physiogel Cream (Glycerol) is a pro-drug of PBA. Upon oral ingestion, PBA is released from the Physiogel Cream (Glycerol) backbone in the gastrointestinal tract by lipases. PBA derived from Physiogel Cream (Glycerol) is further converted by β-oxidation to PAA.

In healthy, fasting adult subjects receiving a single oral dose of 2.9 mL/m² of Physiogel Cream (Glycerol), peak plasma levels of PBA, PAA, and PAGN occurred at 2 hours, 4 hours, and 4 hours, respectively. Upon single-dose administration of Physiogel Cream (Glycerol), plasma concentrations of PBA were quantifiable in 15 of 22 participants at the first sample time postdose (0.25 hours). Mean maximum concentration (C_max) for PBA, PAA, and PAGN was 37.0 micrograms/mL, 14.9 micrograms/mL, and 30.2 micrograms/mL, respectively. In healthy subjects, intact Physiogel Cream (Glycerol) phenylbutyrate was detected in plasma. While the study was inconclusive, the incomplete hydrolysis of Physiogel Cream (Glycerol) phenylbutyrate cannot be ruled out.

In healthy subjects, the systemic exposure to PAA, PBA, and PAGN increased in a dose-dependent manner. Following 4 mL of Physiogel Cream (Glycerol) 3 times a day for 3 days, the mean C_max and AUC were 66 micrograms/mL and 930 micrograms∙h/mL for PBA and 28 micrograms/mL and 942 micrograms∙h/mL for PAA, respectively. In the same study, following 6 mL of Physiogel Cream (Glycerol) three times a day for 3 days, mean C_max and AUC were 100 micrograms/mL and 1400 micrograms∙h/mL for PBA and 65 µg/mL and 2064 micrograms∙h/mL for PAA, respectively.

In adult patients with UCDs receiving multiple doses of Physiogel Cream (Glycerol), maximum plasma concentrations at steady state (C_max,ss) of PBA, PAA, and PAGN occurred at 8 hours, 12 hours, and 10 hours, respectively, after the first dose in the day. Intact Physiogel Cream (Glycerol) phenylbutyrate was not detectable in plasma in patients with UCDs.

Distribution

In vitro, the extent of plasma protein binding for ¹⁴C-labeled metabolites was 81% to 98% for PBA (over 1 to 250 micrograms/mL), and 37% to 66% for PAA (over 5 to 500 micrograms/mL). The protein binding for PAGN was 7% to 12% and no concentration effects were noted.

Elimination

Metabolism

Upon oral administration, pancreatic lipases hydrolyze Physiogel Cream (Glycerol) (i.e., Physiogel Cream (Glycerol) phenylbutyrate), and release PBA. PBA undergoes β-oxidation to PAA, which is conjugated with glutamine in the liver and in the kidney through the enzyme phenylacetyl-CoA: L-glutamine-N-acetyltransferase to form PAGN. PAGN is subsequently eliminated in the urine.

Saturation of conjugation of PAA and glutamine to form PAGN was suggested by increases in the ratio of plasma PAA to PAGN with increasing dose and with increasing severity of hepatic impairment.

In healthy subjects, after administration of 4 mL, 6 mL, and 9 mL 3 times daily for 3 days, the ratio of mean AUC_0-23h of PAA to PAGN was 1, 1.25, and 1.6, respectively. In a separate study, in patients with hepatic impairment (Child-Pugh B and C), the ratios of mean C_max values for PAA to PAGN among all patients dosed with 6 mL and 9 mL twice daily were 3 and 3.7.

In in vitro studies, the specific activity of lipases for Physiogel Cream (Glycerol) phenylbutyrate was in the following decreasing order: pancreatic triglyceride lipase, carboxyl ester lipase, and pancreatic lipase–related protein 2. Further, Physiogel Cream (Glycerol) phenylbutyrate was hydrolyzed in vitro by esterases in human plasma. In these in vitro studies, a complete disappearance of Physiogel Cream (Glycerol) phenylbutyrate did not produce molar equivalent PBA, suggesting the formation of mono- or bis-ester metabolites. However, the formation of mono- or bis-esters was not studied in humans.

Excretion

The mean (SD) percentage of administered PBA excreted as PAGN was approximately 69% (17) in adults and 66% (24) in pediatric patients with UCDs at steady state. PAA and PBA represented minor urinary metabolites, each accounting for less than 1% of the administered dose of PBA.

Specific Populations

Age: Pediatric Population

Population pharmacokinetic modeling and dosing simulations suggest body surface area to be the most significant covariate explaining the variability of PAA clearance. PAA clearance was 10.9 L/h, 16.4 L/h, and 24.4 L/h, respectively, for patients ages 3 to 5, 6 to 11, and 12 to 17 years with UCDs.

In pediatric patients with UCDs (n = 14) ages 2 months to less than 2 years, PAA clearance was 6.8 L/h.

Sex

In healthy adult subjects, a gender effect was found for all metabolites, with women generally having higher plasma concentrations of all metabolites than men at a given dose level. In healthy female subjects, mean C_max for PAA was 51 and 120% higher than in male volunteers after administration of 4 mL and 6 mL 3 times daily for 3 days, respectively. The dose normalized mean AUC_0-23h for PAA was 108% higher in females than in males.

Renal Impairment

The pharmacokinetics of Physiogel Cream (Glycerol) in patients with impaired renal function, including those with end-stage renal disease (ESRD) or those on hemodialysis, have not been studied .

Hepatic Impairment

The effects of hepatic impairment on the pharmacokinetics of Physiogel Cream (Glycerol) were studied in patients with mild, moderate and severe hepatic impairment of (Child-Pugh class A, B, and C, respectively) receiving 100 mg/kg of Physiogel Cream (Glycerol) twice daily for 7 days.

Plasma Physiogel Cream (Glycerol) phenylbutyrate was not measured in patients with hepatic impairment.

After multiple doses of Physiogel Cream (Glycerol) in patients with hepatic impairment of Child-Pugh A, B, and C, geometric mean AUC_t of PBA was 42%, 84%, and 50% higher, respectively, while geometric mean AUC_t of PAA was 22%, 53%, and 94% higher, respectively, than in healthy subjects.

In patients with hepatic impairment of Child-Pugh A, B, and C, geometric mean AUC_t of PAGN was 42%, 27%, and 22% lower, respectively, than that in healthy subjects.

The proportion of PBA excreted as PAGN in the urine in Child-Pugh A, B, and C was 80%, 58%, and 85%, respectively, and, in healthy volunteers, was 67%.

In another study in patients with moderate and severe hepatic impairment (Child-Pugh B and C), mean C_max of PAA was 144 micrograms/mL (range: 14 to 358 micrograms/mL) after daily dosing of 6 mL of Physiogel Cream (Glycerol) twice daily, while mean C_max of PAA was 292 micrograms/mL (range: 57 to 655 micrograms/mL) after daily dosing of 9 mL of Physiogel Cream (Glycerol) twice daily. The ratio of mean C_max values for PAA to PAGN among all patients dosed with 6 mL and 9 mL twice daily were 3 and 3.7, respectively.

After multiple doses, a PAA concentration greater than 200 micrograms/mL was associated with a ratio of plasma PAA to PAGN concentrations higher than 2.5 .

Drug Interaction Studies

In vitro PBA or PAA did not induce CYP1A2, suggesting that in vivo drug interactions via induction of CYP1A2 is unlikely.

In in vitro studies, PBA at a concentration of 800 micrograms/mL caused greater than 60% reversible inhibition of cytochrome P450 isoenzymes CYP2C9, CYP2D6, and CYP3A4/5 (testosterone 6β-hydroxylase activity). The in vitro study suggested that in vivo drug interactions with substrates of CYP2D6 cannot be ruled out. The inhibition of CYP isoenzymes 1A2, 2C8, 2C19, and 2D6 by PAA at the concentration of 2.8 mg/mL was observed in vitro. Clinical implication of these results is unknown.

Effects of Physiogel Cream (Glycerol) on other drugs

Midazolam

In healthy subjects, when oral midazolam was administered after multiple doses of Physiogel Cream (Glycerol) (4 mL three times a day for 3 days) under fed conditions, the mean C_max and AUC for midazolam were 25% and 32% lower, respectively, compared to administration of midazolam alone. In addition the mean C_max and AUC for 1-hydroxy midazolam were 28% and 58% higher, respectively, compared to administration of midazolam alone .

Celecoxib

Concomitant administration of Physiogel Cream (Glycerol) did not significantly affect the pharmacokinetics of celecoxib, a substrate of CYP2C9. When 200 mg of celecoxib was orally administered with Physiogel Cream (Glycerol) after multiple doses of Physiogel Cream (Glycerol) (4 mL three times a day for 6 days) under fed conditions (a standard breakfast was consumed 5 minutes after celecoxib administration), the mean C_max and AUC for celecoxib were 13% and 8% lower than after administration of celecoxib alone.

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis

In a 2-year study in Sprague-Dawley rats, Physiogel Cream (Glycerol) phenylbutyrate caused a statistically significant increase in the incidence of pancreatic acinar cell adenoma, carcinoma, and combined adenoma or carcinoma at a dose of 650 mg/kg/day in males (4.7 times the dose of 6.9 mL/m²/day in adult patients, based on combined AUCs for PBA and PAA) and 900 mg/kg/day in females (8.4 times the dose of 6.9 mL/m²/day in adult patients, based on combined AUCs for PBA and PAA). The incidence of the following tumors was also increased in female rats at a dose of 900 mg/kg/day: thyroid follicular cell adenoma, carcinoma and combined adenoma or carcinoma, adrenal cortical combined adenoma or carcinoma, uterine endometrial stromal polyp, and combined polyp or sarcoma. The dose of 650 mg/kg/day in male rats is 3 times the dose of 7.5 mL/m²/day in pediatric patients, based on combined AUCs for PBA and PAA. The dose of 900 mg/kg/day in female rats is 5.5 times the dose of 7.5 mL/m²/day in pediatric patients, based on combined AUCs for PBA and PAA. In a 26-week study in transgenic (Tg.rasH2) mice, Physiogel Cream (Glycerol) phenylbutyrate was not tumorigenic at doses up to 1000 mg/kg/day.

Mutagenesis

Physiogel Cream (Glycerol) phenylbutyrate was not genotoxic in the Ames test, the in vitro chromosomal aberration test in human peripheral blood lymphocytes, or the in vivo rat micronucleus test. The metabolites PBA, PAA, PAGN, and phenylacetylglycine were not genotoxic in the Ames test or in vitro chromosome aberration test in Chinese hamster ovary cells.

Impairment of Fertility

Physiogel Cream (Glycerol) phenylbutyrate had no effect on fertility or reproductive function in male and female rats at oral doses up to 900 mg/kg/day. At doses of 1200 mg/kg/day (approximately 7 times the dose of 6.9 mL/m²/day in adult patients, based on combined AUCs for PBA and PAA), maternal toxicity was observed and the number of nonviable embryos was increased.

14 CLINICAL STUDIES

14.1 Clinical Studies in Adult Patients with UCDs

Active-Controlled, 4-Week, Noninferiority Study

A randomized, double-blind, active-controlled, crossover, noninferiority study (Study 1) compared Physiogel Cream (Glycerol) to sodium phenylbutyrate by evaluating venous ammonia levels in patients with UCDs who had been on sodium phenylbutyrate prior to enrollment for control of their UCD. Patients were required to have a confirmed diagnosis of UCD involving deficiencies of CPS, OTC, or ASS, confirmed via enzymatic, biochemical, or genetic testing. Patients had to have no clinical evidence of hyperammonemia at enrollment and were not allowed to receive drugs known to increase ammonia levels (e.g., valproate), increase protein catabolism (e.g., corticosteroids), or significantly affect renal clearance (e.g., probenecid).

The primary endpoint was the 24-hour AUC (a measure of exposure to ammonia over 24 hours) for venous ammonia on days 14 and 28 when the drugs were expected to be at steady state. Statistical noninferiority would be established if the upper limit of the 2-sided 95% CI for the ratio of the geometric means (RAVICTI/sodium phenylbutyrate) for the endpoint was 1.25 or less.

Forty-five patients were randomized 1:1 to 1 of 2 treatment arms to receive either

• Sodium phenylbutyrate for 2 weeks → Physiogel Cream (Glycerol) for 2 weeks; or
• Physiogel Cream (Glycerol) for 2 weeks → sodium phenylbutyrate for 2 weeks.

Sodium phenylbutyrate or Physiogel Cream (Glycerol) were administered three times daily with meals. The dose of Physiogel Cream (Glycerol) was calculated to deliver the same amount of PBA as the sodium phenylbutyrate dose the patients were taking when they entered the study. Forty-four patients received at least 1 dose of Physiogel Cream (Glycerol) in the study.

Patients adhered to a low-protein diet and received amino acid supplements throughout the study. After 2 weeks of dosing, by which time patients had reached steady state on each treatment, all patients had 24 hours of ammonia measurements.

Demographic characteristics of the 45 patients enrolled in Study 1 were as follows: mean age at enrollment was 33 years (range: 18 to 75 years); 69% were female; 33% had adult-onset disease; 89% had OTC deficiency; 7% had ASS deficiency; 4% had CPS deficiency.

Physiogel Cream (Glycerol) was non-inferior to sodium phenylbutyrate with respect to the 24-hour AUC for ammonia. Forty-four patients were evaluated in this analysis. Mean 24-hour AUCs for venous ammonia during steady-state dosing were 866 micromol∙h/L and 977 micromol∙h/L with Physiogel Cream (Glycerol) and sodium phenylbutyrate, respectively. The ratio of geometric means was 0.91 [95% CI 0.8, 1.04].

The mean venous ammonia levels over 24-hours after 2 weeks of dosing (on day 14 and 28) in the double-blind short-term study (Study 1) are displayed in Figure 2 below. The mean and median maximum venous ammonia concentration (C_max) over 24 hours and 24-hour AUC for venous ammonia are summarized in Table 2. Ammonia values across different laboratories were normalized to a common normal range of 9 to 35 micromol/L using the following formula after standardization of the units to micromol/L:

Normalized ammonia (micromol/L) = ammonia readout in micromol/L × (35/ULN of a laboratory reference range specified for each assay)

Figure 2: Venous Ammonia Response in Adult Patients with UCDs in Short-Term Treatment Study 1

Open-Label, Uncontrolled, Extension Study in Adults

A long-term (12-month), uncontrolled, open-label study (Study 2) was conducted to assess monthly ammonia control and hyperammonemic crisis over a 12-month period. A total of 51 adults were in the study and all but 6 had been converted from sodium phenylbutyrate to Physiogel Cream (Glycerol). Venous ammonia levels were monitored monthly. Mean fasting venous ammonia values in adults in Study 2 were within normal limits during long-term treatment with Physiogel Cream (Glycerol) (range: 6 to 30 micromol/L). Of 51 adult patients participating in the 12-month, open-label treatment with Physiogel Cream (Glycerol), 7 patients (14%) reported a total of 10 hyperammonemic crises. The fasting venous ammonia measured during Study 2 is displayed in Figure 3. Ammonia values across different laboratories were normalized to a common normal range of 9 to 35 micromol/L.

Figure 3: Venous Ammonia Response in Adult Patients with UCDs in Long-Term Treatment Study 2

Open-Label, Long-Term Study in Adults

An open-label long-term, study (Study 5) was conducted to assess ammonia control in adult patients with UCDs. The study enrolled patients with UCDs who had completed the safety extensions of Study 1, Study 3 or Study 4 (Study 2, 3E and 4E, respectively). A total of 43 adult patients between the ages of 19 and 61 years were in the study. The median length of study participation was 1.9 years (range 0 to 4.5 years). Venous ammonia levels were monitored at a minimum of every 6 months. Mean fasting venous ammonia values in adult patients in Study 5 were within normal limits during long-term (24 months) treatment with Physiogel Cream (Glycerol) (range: 24.2 to 31.4 micromol/L). Of the 43 adult patients participating in the open-label treatment with Physiogel Cream (Glycerol), 9 patients (21%) reported a total of 21 hyperammonemic crises. Ammonia values across different laboratories were normalized to a common normal range of 10 to 35 micromol/L.

14.2 Clinical Studies in Pediatric Patients Ages 2 to 17 Years with UCDs

The efficacy of Physiogel Cream (Glycerol) in pediatric patients 2 to 17 years of age with UCDs was evaluated in 2 fixed-sequence, open-label, sodium phenylbutyrate to Physiogel Cream (Glycerol) switchover studies (Studies 3 and 4). Study 3 was 7 days in duration and Study 4 was 10 days in duration.

These studies compared blood ammonia levels of patients on Physiogel Cream (Glycerol) to venous ammonia levels of patients on sodium phenylbutyrate in 26 pediatric patients between 2 months and 17 years of age with UCDs. Four patients less than 2 years of age are excluded for this analysis due to insufficient data. The dose of Physiogel Cream (Glycerol) was calculated to deliver the same amount of PBA as the dose of sodium phenylbutyrate patients were taking when they entered the trial. Sodium phenylbutyrate or Physiogel Cream (Glycerol) were administered in divided doses with meals. Patients adhered to a low-protein diet throughout the study. After a dosing period with each treatment, all patients underwent 24 hours of venous ammonia measurements, as well as blood and urine pharmacokinetic assessments.

UCD subtypes included OTC (n=12), argininosuccinate lyase (ASL) (n=8), and ASS deficiency (n=2), and patients received a mean Physiogel Cream (Glycerol) dose of 8 mL/m²/day (8.8 g/m²/day), with doses ranging from 1.4 to 13.1 mL/m²/day (1.5 to 14.4 g/m²/day). Doses in these patients were based on previous dosing of sodium phenylbutyrate.

The 24-hour AUCs for blood ammonia (AUC_0-24h) in 11 pediatric patients 6 to 17 years of age with UCDs (Study 3) and 11 pediatric patients 2 years to 5 years of age with UCDs (Study 4) were similar between treatments. In children 6 to 17 years of age, the ammonia AUC_0-24h was 604 micromol∙h/L vs 815 micromol∙h/L on Physiogel Cream (Glycerol) vs sodium phenylbutyrate. In the patients between 2 years and 5 years of age with UCDs, the ammonia AUC_0-24h was 632 micromol∙h/L vs 720 micromol∙h/L on Physiogel Cream (Glycerol) versus sodium phenylbutyrate.

The mean venous ammonia levels over 24 hours in open-label, short-term Studies 3 and 4 at common time points are displayed in Figure 4. Ammonia values across different laboratories were normalized to a common normal range of 9 to 35 micromol/L using the following formula after standardization of the units to micromol/L:

Normalized ammonia (micromol/L) = ammonia readout in micromol/L × (35/ULN of a laboratory reference range specified for each assay)

Figure 4: Venous Ammonia Response in Pediatric Patients Ages 2 to 17 Years with UCDs in Short-Term Treatment Studies 3 and 4

Open-Label, Uncontrolled, Extension Studies in Children Ages 2 to 17 Years

Long-term (12-month), uncontrolled, open-label studies were conducted to assess monthly ammonia control and hyperammonemic crisis over a 12-month period. In two studies (Study 2, which also enrolled adults, and an extension of Study 3, referred to here as Study 3E), a total of 26 children ages 6 to 17 were enrolled and all but 1 had been converted from sodium phenylbutyrate to Physiogel Cream (Glycerol). Mean fasting venous ammonia values were within normal limits during long-term treatment with Physiogel Cream (Glycerol) (range: 17 to 23 micromol/L). Of the 26 pediatric patients 6 to 17 years of age participating in these two trials, 5 patients (19%) reported a total of 5 hyperammonemic crises. The fasting venous ammonia measured during these two extension studies in patients 6 to 17 years is displayed in Figure 5. Ammonia values across different laboratories were normalized to a common normal range of 9 to 35 micromol/L.

Figure 5: Venous Ammonia Response in Pediatric Patients Ages 2 to 17 Years with UCDs in Long-Term Treatment Studies 2 and 3E

In an extension of Study 4, after a median time on study of 4.5 months (range: 1 to 5.7 months), 2 of 16 pediatric patients ages 2 to 5 years had experienced three hyperammonemic crises.

Open-Label, Long-Term Study in Children Ages 1 to 17 Years of Age

An open-label, long-term study (Study 5) was conducted to assess ammonia control in pediatric patients with UCD. The study enrolled patients with UCD who had completed the safety extensions of Study 1, Study 3 or Study 4 (Study 2, 3E and 4E, respectively). A total of 45 pediatric patients between the ages of 1 and 17 years were in the study. The median length of study participation was 1.7 years (range 0.2 to 4.6 years). Venous ammonia levels were monitored at a minimum of every 6 months. Mean venous ammonia values in pediatric patients in Study 5 were within normal limits during long-term (24 months) treatment with Physiogel Cream (Glycerol) (range: 15.4 to 25.1 micromol/L). Of the 45 pediatric patients participating in the open-label treatment with Physiogel Cream (Glycerol), 11 patients (24%) reported a total of 22 hyperammonemic crises. Ammonia values across different laboratories were normalized to a common normal range of 10 to 35 micromol/L.

14.3 Clinical Studies in Pediatric Patients Ages 2 Months to Less Than 2 Years with UCDs

Uncontrolled, open-label studies were conducted to assess monthly ammonia control and hyperammonemic crisis of Physiogel Cream (Glycerol) in pediatric patients with UCDs 2 months to less than 2 years of age (Study 4/4E, Study 5, and Study 6). Patients in Study 5 previously participated in Study 4/4E. A total of 17 pediatric patients with UCDs aged 2 months to less than 2 years participated in the studies.

Uncontrolled, Open-Label Study in Children Under 2 Years of Age (Study 6)

A total of 10 pediatric patients with UCDs aged 2 months to less than 2 years participated in Study 6, of which 7 patients converted from sodium phenylbutyrate to Physiogel Cream (Glycerol). The dosage of Physiogel Cream (Glycerol) was calculated to deliver the same amount of PBA as the sodium phenylbutyrate dosage the patients were taking when they entered the trial. Two patients were treatment naïve and received Physiogel Cream (Glycerol) dosage of 7.5 mL/m²/day and 9.4 mL/m²/day, respectively. One additional patient was gradually discontinued from intravenous sodium benzoate and sodium phenylacetate while Physiogel Cream (Glycerol) was initiated. The dosage of Physiogel Cream (Glycerol) after transition was 8.5 mL/m²/day.

In Study 6, there were 9, 7 and 3 pediatric patients who completed 1, 3 and 6 months, respectively (mean and median exposure of 4 and 5 months, respectively).

Patients received a mean Physiogel Cream (Glycerol) dose of 8 mL/m²/day (8.8 g/m²/day), with doses ranging from 4.8 to 11.5 mL/m²/day (5.3 to 12.6 g/m²/day). Patients were dosed three times a day (n=6), four times a day (n = 2), or five or more times a day (n=2).

The primary efficacy endpoint was successful transition to Physiogel Cream (Glycerol) within a period of 4 days followed by 3 days of observation for a total of 7 days, where successful transition was defined as no signs and symptoms of hyperammonemia and a venous ammonia value less than 100 micromol/L. Venous ammonia levels were monitored for up to 4 days during transition and on day 7. Nine patients successfully transitioned as defined by the primary endpoint. One additional patient developed hyperammonemia on day 3 of dosing and experienced surgical complications (bowel perforation and peritonitis) following jejunal tube placement on day 4. This patient developed hyperammonemic crisis on day 6, and subsequently died of sepsis from peritonitis unrelated to drug. Although two patients had day 7 ammonia values of 150 micromol/L and 111 micromol/L respectively, neither had associated signs and symptoms of hyperammonemia.

During the extension phase, venous ammonia levels were monitored monthly. Ammonia values across different laboratories were normalized (transformed) to a common normal pediatric range of 28 to 57 micromol/L for comparability. The mean normalized venous ammonia values in pediatric patients at month 1, 2, 3, 4, 5 and 6 were 67, 53, 78, 99, 56 and 61 micromol/L during treatment with Physiogel Cream (Glycerol), respectively. Three patients reported a total of 7 hyperammonemic crises defined as having signs and symptoms consistent with hyperammonemia (such as frequent vomiting, nausea, headache, lethargy, irritability, combativeness, and/or somnolence) associated with high venous ammonia levels and requiring medical intervention. Hyperammonemic crises were precipitated by vomiting, upper respiratory tract infection, gastroenteritis, decreased caloric intake or had no identified precipitating event (3 events). There were three additional patients who had one venous ammonia level that exceeded 100 micromol/L which was not associated with a hyperammonemic crisis.

Uncontrolled, Open-Label Studies in Children Under 2 Years of Age (Studies 4/4E, 5)

A total of 7 patients with UCDs aged 2 months to less than 2 years participated in Studies 4/4E and 5. In these studies, there were 7, 6, 6, 6 and 3 pediatric patients who completed 1, 6, 9, 12 and 18 months, respectively (mean and median exposure of 15 and 17 months, respectively). Patients were converted from sodium phenylbutyrate to Physiogel Cream (Glycerol). The dosage of Physiogel Cream (Glycerol) was calculated to deliver the same amount of PBA as the sodium phenylbutyrate dosage the patients were taking when they entered the study.

Patients received a mean Physiogel Cream (Glycerol) dose of 7.5 mL/m²/day (8.2 g/m²/day), with doses ranging from 3.3 to 12.3 mL/m²/day (3.7 to 13.5 g/m²/day). Patients were dosed three times a day (n=3) or four times a day (n = 4).

Venous ammonia levels were monitored on days 1, 3 and 10 in Study 4 and at week 1 in Study 4E. Two patients had day 1 ammonia values of 122 micromol/L and 111 micromol/L respectively, neither had associated signs and symptoms of hyperammonemia. At day 10/week 1, six of the 7 patients had venous ammonia levels less than 100 micromol/L the remaining patient had a day 10 ammonia value of 168 micromol/L and was asymptomatic.

During the extension period, venous ammonia levels were monitored monthly. Ammonia values across different laboratories were normalized (transformed) to a common normal pediatric range of 28 to 57 micromol/L for comparability. The mean venous ammonia values in pediatric patients at month 1, 3, 6, 9 and 12 were 58, 49, 34, 65, and 31 micromol/L during treatment with Physiogel Cream (Glycerol), respectively.

Three patients reported a total of 3 hyperammonemic crises, as defined in Study 6. Hyperammonemic crises were precipitated by gastroenteritis, vomiting, infection or no precipitating event (one patient). There were 4 patients who had one venous ammonia level that exceeded 100 micromol/L which was not associated with a hyperammonemic crisis.

16 HOW SUPPLIED/STORAGE AND HANDLING

Physiogel Cream (Glycerol) ^® (glycerol phenylbutyrate) oral liquid 1.1 g/mL is supplied in multi-use, 25-mL glass bottles. The bottles are supplied in the following configurations:

• NDC 75987-050-06: Single 25-mL bottle per carton
• NDC 75987-050-07: Four 25-mL bottles per carton

Store at 20°-25°C (68°-77°F) with excursions permitted to 15°-30°C (59°-86°F).

17 PATIENT COUNSELING INFORMATION

Advise the patient to read the FDA-approved patient labeling (Medication Guide).

Neurotoxicity .

• Inform patients/caregivers that adverse reactions of Physiogel Cream (Glycerol) are sometimes the same as symptoms of high blood ammonia. Neurological adverse events may also be associated with the major metabolite of Physiogel Cream (Glycerol), PAA, and may be reversible. Blood tests for PAA may be done to measure the amount of PAA in the blood. Instruct the patient/caregiver to contact the healthcare provider immediately if the patient experiences: nausea, vomiting, headache, fatigue, somnolence, lightheadedness, confusion, exacerbation of preexisting neuropathy, disorientation, impaired memory, dysgeusia, or hypoacusis.

Pregnancy Registry

Advise patients that there is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to Physiogel Cream (Glycerol) during pregnancy .

Lactation

Advise patients that breastfeeding is not recommended during treatment with Physiogel Cream (Glycerol) .

Administration

• Instruct patients to take Physiogel Cream (Glycerol) with food or formula and to administer directly into the mouth via oral syringe or dosing cup.
• Instruct patients to take Physiogel Cream (Glycerol) orally, even if they have a nasogastric and/or gastrostomy tube. For patients who cannot swallow and who have a nasogastric tube or gastrostomy tube in place, instruct patients/caregivers to administer Physiogel Cream (Glycerol) as follows:
  • Utilize an oral syringe to withdraw the prescribed dosage of Physiogel Cream (Glycerol) from the bottle.
  • Place the tip of the syringe into the gastrostomy/nasogastric tube.
  • Utilizing the plunger of the syringe, administer Physiogel Cream (Glycerol) into the tube.
  • Flush once with 10 mL of water or formula and allow the flush to drain.
  • If needed, flush a second time with an additional 10 mL of water or formula to clear the tube.

Distributed by:

Horizon Pharma USA, Inc.

Lake Forest, IL 60045

Horizon Therapeutics, LLC.

All rights reserved.

Physiogel Cream (Glycerol) is a registered trademark of Horizon Therapeutics, LLC.