Phenylacetate

1 INDICATIONS AND USAGE Sodium Phenylacetate and Sodium Benzoate Injection is a nitrogen binding agent indicated as adjunctive therapy for the treatment of acute hyperammonemia and associated encephalopathy in paediatric and adult patients with deficiencies in enzymes of the urea cycle. ( 1 ) Sodium Phenylacetate and Sodium Benzoate Injection is indicated as adjunctive therapy in pediatric and adult patients for the treatment of acute hyperammonemia and associated encephalopathy in patients with deficiencies in enzymes of the urea cycle. During acute hyperammonemic episodes, arginine supplementation, caloric supplementation, dietary protein restriction, hemodialysis, and other ammonia lowering therapies should be considered [ see Warnings and Precautions (5) ].

12.1 Mechanism of Action Urea cycle disorders can result from decreased activity of any of the following enzymes: N -acetylglutamate synthetase (NAGS), carbamyl phosphate synthetase (CPS), argininosuccinate synthetase (ASS), ornithine transcarbamylase (OTC), argininosuccinate lyase (ASL), or arginase (ARG). Sodium phenylacetate and sodium benzoate are metabolically active compounds that can serve as alternatives to urea for the excretion of waste nitrogen. Figure 2 is a schematic illustrating how the components of Sodium Phenylacetate and Sodium Benzoate Injection, phenylacetate and benzoate, provide an alternative pathway for nitrogen disposal in patients without a fully functioning urea cycle. Phenylacetate conjugates with glutamine in the liver and kidneys to form phenylacetylglutamine, via acetylation. Phenylacetylglutamine is excreted by the kidneys via glomerular filtration and tubular secretion. The nitrogen content of phenylacetylglutamine per mole is identical to that of urea (both contain two moles of nitrogen). Two moles of nitrogen are removed per mole of phenylacetate when it is conjugated with glutamine. Similarly, preceded by acylation, benzoate conjugates with glycine to form hippuric acid, which is rapidly excreted by the kidneys by glomerular filtration and tubular secretion. One mole of hippuric acid contains one mole of waste nitrogen. Thus, one mole of nitrogen is removed per mole of benzoate when it is conjugated with glycine. Figure 2 CPS = carbamyl phosphate synthetase; OTC = ornithine transcarbamylase; ASS = argininosuccinate synthetase; ASL = argininosuccinate lyase; ARG = arginase; NAGS = N -acetylglutamate synthetase

2 DOSAGE AND ADMINISTRATION Sodium Phenylacetate and Sodium Benzoate Injection must be diluted with sterile 10% Dextrose Injection (D10W) before administration. Administration must be through a central venous catheter. Administration through a peripheral line may cause burns. ( 2 ) Sodium Phenylacetate and Sodium Benzoate Injection is administered intravenously as a loading dose infusion administered over 90 to 120 minutes, followed by an equivalent maintenance dose infusion administered over 24 hours. ( 2 ) See Full Prescribing Information for complete dosing recommendations. 2.1 Recommended Dosage Sodium Phenylacetate and Sodium Benzoate Injection must be diluted with sterile 10% Dextrose Injection (D10W) before administration. The dilution and dosage of Sodium Phenylacetate and Sodium Benzoate Injection are determined by weight for neonates, infants and young children, and by body surface area for larger patients, including older children, adolescents, and adults (Table 1). Table 1: Dosage and Administration Abbreviations: CPS - carbamyl phosphate synthetase; OTC - ornithine transcarbamylase; ASS - argininosuccinate synthetase; ASL - argininosuccinate lyase Patient Population Components of Infusion Solution Sodium Phenylacetate and Sodium Benzoate Injection must be diluted with sterile 10% Dextrose Injection at ≥ 25 mL/Kg before administration. Dosage Provided Sodium Phenylacetate and Sodium Benzoate Injection Arginine HCl Injection, 10% Sodium Phenylacetate Sodium Benzoate Arginine HCl CPS and OTC Deficiency Patients 0 to 20 kg: Dose Loading: over 90 to 120 minutes Maintenance: over 24 hours 2.5 mL/kg 2 mL/kg 250 mg/kg 250 mg/kg 200 mg/kg ASS and ASL Deficiency Dose Loading: over 90 to 120 minutes Maintenance: over 24 hours 2.5 mL/kg 6 mL/kg 250 mg/kg 250 mg/kg 600 mg/kg CPS and OTC Deficiency Patient>20kg: Dose Loading: over 90 to 120 minutes Maintenance: over 24 hours 55 mL/m 2 2 mL/kg 5.5g/m 2 5.5 g/m 2 200 mg/kg ASS and ASL Deficiency Dose Loading: over 90 to 120 minutes Maintenance: over 24 hours 55 mL/m 2 6 mL/kg 5.5 g/m 2 5.5 g/m 2 600 mg/kg 2.2 Administration Sodium Phenylacetate and Sodium Benzoate Injection is a concentrated solution and must be diluted before intravenous administration via a central venous catheter. Administration through a peripheral intravenous catheter may cause burns. Sodium Phenylacetate and Sodium Benzoate Injection may not be administered by any other route. Sodium Phenylacetate and Sodium Benzoate Injection should be administered as a loading dose infusion over 90 to 120 minutes, followed by the same dose repeated as a maintenance infusion administered over 24 hours. Because of prolonged plasma levels achieved by phenylacetate in pharmacokinetic studies, repeat loading doses of Sodium Phenylacetate and Sodium Benzoate Injection should not be administered. Maintenance infusions may be continued until elevated plasma ammonia levels have been normalized or the patient can tolerate oral nutrition and medications. An antiemetic may be administered during Sodium Phenylacetate and Sodium Benzoate Injection infusion to aid control of infusion-associated nausea and vomiting. Administration of analogous oral drugs, such as sodium phenylbutyrate, should be terminated prior to Sodium Phenylacetate and Sodium Benzoate Injection infusion. Sodium Phenylacetate and Sodium Benzoate Injection infusion should be started as soon as the diagnosis of hyperammonemia is made. Treatment of hyperammonemia also requires caloric supplementation and restriction of dietary protein. Non-protein calories should be supplied principally as glucose (8–10 mg/kg/min) with an intravenous fat emulsion added. Attempts should be made to maintain a caloric intake of greater than 80 kcal/kg/day. During and after infusion of Sodium Phenylacetate and Sodium Benzoate Injection, ongoing monitoring of the following clinical laboratory values is crucial: plasma ammonia, glutamine, quantitative plasma amino acids, blood glucose, electro

6 ADVERSE REACTIONS The most frequently reported adverse reactions (incidence ≥ 6%) are vomiting, hyperglycemia, hypokalemia, convulsions, and mental impairment. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Zydus Pharmaceuticals USA Inc. Pennington, NJ 08534 at 1-877-993-8779 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 practice. The safety data were obtained from 316 patients who received Sodium Phenylacetate and Sodium Benzoate Injection as emergency (rescue) or prospective treatment for hyperammonemia as part of an uncontrolled, open-label study. The study population included patients between the ages of 0 to 53 years with a mean (SD) of 6.2 (8.54) years; 51% were male and 49% were female who had the following diagnoses: OTC (46%), ASS (22%), CPS (12%), ASL (2%), ARG (<1%), THN (<1%), and other (18%). Adverse reactions were reported with similar frequency in patients with OTC, ASS, CPS, and diagnoses categorized as "other." Nervous system disorders were more frequent in patients with OTC and CPS, compared with patients with ASS and patients with "other" diagnoses. Convulsions and mental impairment were reported in patients with OTC and CPS. These observations are consistent with literature reports that patients with enzyme deficiencies occurring earlier in the urea cycle (i.e., OTC and CPS) tend to be more severely affected. Adverse reactions profiles differed by age group. Patients ≤30 days of age had more blood and lymphatic system disorders and vascular disorders (specifically hypotension), while patients > 30 days of age had more gastrointestinal disorders (specifically nausea, vomiting and diarrhea). Less common adverse reactions (<3% of patients) that are characterized as severe are listed below by body system. BLOOD AND LYMPHATIC SYSTEM DISORDERS: coagulopathy, pancytopenia, thrombocytopenia. CARDIAC DISORDERS: atrial rupture, bradycardia, cardiac or cardiopulmonary arrest/failure, cardiogenic shock, cardiomyopathy, pericardial effusion. EYE DISORDERS: blindness. GASTROINTESTINAL DISORDERS: abdominal distension, gastrointestinal hemorrhage. GENERAL DISORDERS AND ADMINISTRATION-SITE CONDITIONS: asthenia, brain death, chest pain, multiorgan failure, edema. HEPATOBILIARY DISORDERS: cholestasis, hepatic artery stenosis, hepatic failure/hepatotoxicity, jaundice. INFECTIONS AND INFESTATIONS: sepsis/septic shock. INJURY, POISONING AND PROCEDURAL COMPLICATIONS: brain herniation, subdural hematoma, overdose. INVESTIGATIONS: blood carbon dioxide changes, blood glucose changes, blood pH increased, cardiac output decreased, pCO 2 changes, respiratory rate increased. METABOLISM AND NUTRITION DISORDERS: alkalosis, dehydration, fluid overload/retention, hypoglycemia, hyperkalemia, hypernatremia, alkalosis, tetany. NEOPLASMS BENIGN, MALIGNANT AND UNSPECIFIED: hemangioma acquired. NERVOUS SYSTEM DISORDERS: areflexia, ataxia, brain infarction, brain hemorrhage, cerebral atrophy, clonus, depressed level of consciousness, encephalopathy, nerve paralysis, intracranial pressure increased, subdural hematoma, tremor. PSYCHIATRIC DISORDERS: acute psychosis, aggression, confusional state, hallucinations. RENAL AND URINARY DISORDERS: anuria, renal failure, urinary retention. RESPIRATORY, THORACIC AND MEDIASTINAL DISORDERS: acute respiratory distress syndrome, dyspnea, hypercapnia, hyperventilation, Kussmaul respiration, pneumonia aspiration, pneumothorax, pulmonary hemorrhage, pulmonary edema, respiratory acidosis or alkalosis, respiratory arrest/failure. SKIN AND SUBCUTANEOUS TISSUE DISORDERS: alopecia, blister, pruritus generalized, rash, urticarial. VASCULAR DISORDERS: flushing, hemorrhage, hypertension, phlebothrombosis/thrombosis. Table 2 : Adver

5 WARNINGS AND PRECAUTIONS Decreased Potassium Levels: Plasma potassium levels should be carefully monitored and appropriate treatment given when necessary. ( 5.1 ) Conditions Associated with Fluid Overload: Sodium Phenylacetate and Sodium Benzoate Injection contains 30.5 mg of sodium per mL of undiluted product. Caution should be used if Sodium Phenylacetate and Sodium Benzoate Injection is administered to patients with congestive heart failure, severe renal insufficiency, or with conditions in which there is sodium retention with edema. ( 5.2 ) Extravasation: Extravasation of Sodium Phenylacetate and Sodium Benzoate Injection into the perivenous tissues during high flow bolus infusion may lead to skin necrosis, especially in infants. The infusion site must be monitored closely for possible tissue infiltration during drug administration. ( 5.3 ) Neurotoxicity of Phenylacetate: Because of prolonged plasma levels achieved by phenylacetate in pharmacokinetic studies, repeat loading doses should not be administered. Additionally, neurotoxicity related to phenylacetate has been reported in cancer patients. Monitor patients for symptoms of acute neurotoxicity.( 5.4 ) Hyperventilation and Metabolic Acidosis: Sodium Phenylacetate and Sodium Benzoate Injection may cause side effects typically associated with salicylate overdose, such as hyperventilation and metabolic acidosis. Monitor patient blood chemistry profiles and perform frequent blood pH and pCO 2 measurements. ( 5.5 ) 5.1 Decreased Potassium Levels Because urine potassium loss is enhanced by the excretion of the non-reabsorbable anions, phenylacetylglutamine and hippurate, plasma potassium levels should be carefully monitored and appropriate treatment given when necessary. 5.2 Conditions Associated with Fluid Overload Sodium Phenylacetate and Sodium Benzoate Injection contains 30.5 mg of sodium per mL of undiluted product. Thus, Sodium Phenylacetate and Sodium Benzoate Injection should be used with great care, if at all, in patients with congestive heart failure or severe renal insufficiency, and in clinical states in which there is sodium retention with edema. Discontinue administration of Sodium Phenylacetate and Sodium Benzoate Injection, evaluate the patient, and institute appropriate therapeutic countermeasures if an adverse event occurs. 5.3 Extravasation Administration must be through a central venous catheter. Administration through a peripheral line may cause burns . Bolus infusion flow rates are relatively high, especially for infants [ see Dosage and Administration (2) ]. Extravasation of Sodium Phenylacetate and Sodium Benzoate Injection into the perivenous tissues may lead to skin necrosis. If extravasation is suspected, discontinue the infusion and resume at a different infusion site, if necessary. The infusion site must be monitored closely for possible infiltration during drug administration. Do not administer undiluted product. 5.4 Neurotoxicity of Phenylacetate Because of prolonged plasma levels achieved by phenylacetate in pharmacokinetic studies, repeat loading doses of Sodium Phenylacetate and Sodium Benzoate Injection should not be administered. Additionally, neurotoxicity was reported in cancer patients receiving intravenous phenylacetate, 250–300 mg/kg/day for 14 days, repeated at 4-week intervals. Manifestations were predominantly somnolence, fatigue, and lightheadedness, with less frequent headaches, dysgeusia, hypoacusis, disorientation, impaired memory, and exacerbation of a pre-existing neuropathy. The acute onset of symptoms upon initiation of treatment and reversibility of symptoms when the phenylacetate was discontinued suggest a drug effect [ See Animal Toxicology and/or Pharmacology (13.2) ]. 5.5 Hyperventilation and Metabolic Acidosis Due to structural similarities between phenylacetate and benzoate to salicylate, Sodium Phenylacetate and Sodium Benzoate Injection may cause side effects typically associated with salicylate overdose, such as

4 CONTRAINDICATIONS None ( 4 ) None.

10 OVERDOSAGE Overdosage has been reported during Sodium Phenylacetate and Sodium Benzoate Injection treatment in urea cycle-deficient patients. All patients in the uncontrolled open-label study were to be treated with the same dose of Sodium Phenylacetate and Sodium Benzoate Injection. However, some patients received more than the dose level specified in the protocol. In 16 of the 64 deaths, the patient received a known overdose of Sodium Phenylacetate and Sodium Benzoate Injection. Causes of death in these patients included cardiorespiratory failure/arrest (6 patients), hyperammonemia (3 patients), increased intracranial pressure (2 patients), pneumonitis with septic shock and coagulopathy (1 patient), error in dialysis procedure (1 patient), respiratory failure (1 patient), intractable hypotension and probable sepsis (1 patient), and unknown (1 patient). Additionally, other signs of intoxication may include obtundation (in the absence of hyperammonemia), hyperventilation, a severe compensated metabolic acidosis, perhaps with a respiratory component, large anion gap, hypernatremia and hyperosmolarity, progressive encephalopathy, cardiovascular collapse, and death. In case of overdose of Sodium Phenylacetate and Sodium Benzoate Injection, discontinue the drug and institute appropriate emergency medical monitoring and procedures. In severe cases, the latter may include hemodialysis (procedure of choice) or peritoneal dialysis (when hemodialysis is unavailable).