SAPROPTERIN DIHYDROCHLORIDE

Sapropterin dihydrochloride is an orally administered Phenylalanine Hydroxylase activator (or PAH activator). Sapropterin dihydrochloride, the active pharmaceutical ingredient in sapropterin dihydrochloride powder for oral solution, is a synthetic preparation of the dihydrochloride salt of naturally occurring tetrahydrobiopterin (BH4). Sapropterin dihydrochloride is a white to pale yellow color powder. The chemical name of sapropterin dihydrochloride is (6R)-2-amino-6-[(1R,2S)-1,2-dihydroxypropyl]-5,6,7,8-tetrahydro-4(1H)-pteridinone dihydrochloride and the molecular formula is C 9 H 15 N 5 O 3 ·2HCl with a molecular weight of 314.17. Sapropterin dihydrochloride has the following structural formula: Sapropterin dihydrochloride is supplied as powder for oral solution containing 100 mg of sapropterin dihydrochloride (equivalent to 76.8 mg of sapropterin base). Sapropterin dihydrochloride is also supplied as powder for oral solution containing 500 mg of sapropterin dihydrochloride (equivalent to 384 mg of sapropterin base). Sapropterin dihydrochloride powder for oral solution is off-white to yellow in color. Each unit dose packet contains the following inactive ingredients: ascorbic acid, mannitol, potassium citrate monohydrate and sucralose. sapropretinepfossructure

Sapropterin dihydrochloride powder for oral solution is indicated to reduce blood phenylalanine (Phe) levels in adult and pediatric patients one month of age and older with hyperphenylalaninemia (HPA) due to tetrahydrobiopterin-(BH4-) responsive Phenylketonuria (PKU). Sapropterin dihydrochloride powder for oral solution is to be used in conjunction with a Phe-restricted diet. Sapropterin dihydrochloride powder for oral solution is a phenylalanine hydroxylase activator indicated to reduce blood phenylalanine (Phe) levels in adult and pediatric patients one month of age and older with hyperphenylalaninemia (HPA) due to tetrahydrobiopterin-(BH4-) responsive Phenylketonuria (PKU). Sapropterin dihydrochloride powder for oral solution is to be used in conjunction with a Phe-restricted diet. ( 1 )

All patients with PKU who are being treated with sapropterin dihydrochloride powder for oral solution should also be treated with a Phe-restricted diet, including dietary protein and Phe restriction. ( 2.1 ) Starting Dosage • Pediatric patients 1 month to 6 years : The recommended starting dose of sapropterin dihydrochloride powder for oral solution is 10 mg/kg taken once daily. ( 2.1 ) • Patients 7 years and older : The recommended starting dose of sapropterin dihydrochloride powder for oral solution is 10 to 20 mg/kg taken once daily. ( 2.1 ) Dosage Adjustment • Doses of sapropterin dihydrochloride powder for oral solution may be adjusted in the range of 5 to 20 mg/kg taken once daily. ( 2.1 ) • Monitor blood Phe regularly, especially in pediatric patients. ( 2.1 , 5.3 ) Preparation and Administration • Take with a meal. ( 2.2 ) • Swallow oral solution after mixing powder in a small amount of soft foods or dissolving in recommended liquids. See full prescribing information for complete information on mixing with food or liquid. ( 2.2 ) 2.1 Dosage Treatment with sapropterin dihydrochloride powder for oral solution should be directed by physicians knowledgeable in the management of PKU. All patients with PKU who are being treated with sapropterin dihydrochloride powder for oral solution should also be treated with a Phe-restricted diet, including dietary protein and Phe restriction. Starting Dosage Pediatric Patients 1 month to 6 years : The recommended starting dose of sapropterin dihydrochloride powder for oral solution is 10 mg/kg taken once daily. Patients 7 years and older : The recommended starting dose of sapropterin dihydrochloride powder for oral solution is 10 to 20 mg/kg taken once daily. Dosage Adjustment (Evaluation Period) Existing dietary protein and Phe intake should not be modified during the evaluation period. If a 10 mg/kg per day starting dose is used, then response to therapy is determined by change in blood Phe following treatment with sapropterin dihydrochloride powder for oral solution at 10 mg/kg per day for a period of up to 1 month. Blood Phe levels should be checked after 1 week of sapropterin dihydrochloride powder for oral solution treatment and periodically for up to a month. If blood Phe does not decrease from baseline at 10 mg/kg per day, the dose may be increased to 20 mg/kg per day. Patients whose blood Phe does not decrease after 1 month of treatment at 20 mg/kg per day do not show a biochemical response and treatment with sapropterin dihydrochloride powder for oral solution should be discontinued in these patients. If a 20 mg/kg per day starting dose is used, then response to therapy is determined by change in blood Phe following treatment with sapropterin dihydrochloride powder for oral solution at 20 mg/kg per day for a period of 1 month. Blood Phe levels should be checked after 1 week of sapropterin dihydrochloride powder for oral solution treatment and periodically during the first month. Treatment should be discontinued in patients who do not show a biochemical response (blood Phe does not decrease) after 1 month of treatment at 20 mg/kg per day [see Warnings and Precautions (5.4) ] . Once responsiveness to sapropterin dihydrochloride powder for oral solution has been established, the dosage may be adjusted within the range of 5 to 20 mg/kg per day according to biochemical response to therapy (blood Phe). Periodic blood Phe monitoring is recommended to assess blood Phe control, especially in pediatric patients [see Warnings and Precautions (5.3) ] . 2.2 Preparation and Administration Instructions Take sapropterin dihydrochloride powder for oral solution orally with a meal, preferably at the same time each day [see Clinical Pharmacology (12.3) ] . A missed dose should be taken as soon as possible, but two doses should not be taken on the same day. Sapropterin Dihydrochloride Powder for Oral Solution Patients weighing greater than 10 kg Sapropterin dihydrochloride powder for oral solution should be dissolved in 120 to 240 mL of water or apple juice and taken orally within 30 minutes of dissolution. Sapropterin dihydrochloride powder for oral solution may also be stirred in a small amount of soft foods such as apple sauce or pudding. Empty the contents of the packet(s) in water, apple juice, or a small amount of soft foods and mix thoroughly. The powder should dissolve completely. Patients weighing 10 kg or less (use 100 mg packets) For infants weighing 10 kg or less, sapropterin dihydrochloride powder for oral solution can be dissolved in as little as 5 mL of water or apple juice and a portion of this solution corresponding to a 10 mg/kg dose may be administered orally via an oral dosing syringe. Table 1 provides dosing information for infants at the recommended starting dose of 10 mg/kg per day. Refer to Table 2 for dosing information at 20 mg/kg per day if dosage adjustment is needed. Table 1: 10 mg/kg per day Dosing Table for Infants Weighing 10 kg or less Patient Weight (kg) Starting Dose: 10 mg/kg per day * Dose (mg) Sapropterin Dihydrochloride Powder for Oral Solution 100 mg Packets Dissolved † Dilution Volume (mL) ‡ Administered Dose volume (mL) § 1 10 1 10 1 2 20 1 10 2 3 30 1 10 3 4 40 1 10 4 5 50 1 10 5 6 60 1 5 3 7 70 1 5 3.5 8 80 1 5 4 9 90 1 5 4.5 10 100 1 5 5 * Starting dose for infants is 10 mg/kg per day. Dosing information for 20 mg/kg per day is provided in Table 2. † Powder for oral solution provided in single use packets containing 100 mg sapropterin dihydrochloride per packet ‡ Volume of water or apple juice to dissolve sapropterin dihydrochloride powder for oral solution. § Discard remainder of mixture after volume to be administered is drawn. Table 2: 20 mg/kg per day Dosing Table for Infants Weighing 10 kg or less Patient Weight (kg) 20 mg/kg per day Dose (mg) Sapropterin Dihydrochloride Powder for Oral Solution 100 mg Packets * Dissolved Dilution Volume (mL ) † Administered Dose volume (mL) § 1 20 1 5 1 2 40 1 5 2 3 60 1 5 3 4 80 1 5 4 5 100 1 5 5 6 120 2 5 3 7 140 2 5 3.5 8 160 2 5 4 9 180 2 5 4.5 10 200 2 5 5 * Powder for oral solution provided in single use packets containing 100 mg sapropterin dihydrochloride per packet † Volume of water or apple juice to dissolve sapropterin dihydrochloride powder for oral solution. § Discard remainder of mixture after volume to be administered is drawn.

None. None. ( 4 )

Most common adverse reactions (≥4%) are: headache, rhinorrhea, pharyngolaryngeal pain, diarrhea, vomiting, cough, and nasal congestion. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact NorthStar Rx LLC at 1-800-206-7821 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 the rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. PKU Clinical Studies The safety of sapropterin dihydrochloride was evaluated in 7 clinical studies in patients with PKU (aged 1 month to 50 years) [see Clinical Studies (14) ]. In Studies 1 to 4 (controlled and uncontrolled studies), 579 patients with PKU aged 4 to 49 years received sapropterin dihydrochloride in doses ranging from 5 to 20 mg/kg per day for lengths of treatment ranging from 1 to 164 weeks. The patient population was evenly distributed in gender, and approximately 95% of patients were Caucasian. The most common adverse reactions (≥4% of patients) were headache, rhinorrhea, pharyngolaryngeal pain, diarrhea, vomiting, cough, and nasal congestion. The data described in Table 3 reflect exposure of 74 patients with PKU to sapropterin dihydrochloride at doses of 10 to 20 mg/kg per day for 6 to 10 weeks in two double-blind, placebo-controlled clinical trials (Studies 2 and 4). Table 3 enumerates adverse reactions occurring in at least 4% of patients treated with sapropterin dihydrochloride in the double-blind, placebo-controlled clinical trials described above. Table 3: Summary of Adverse Reactions Occurring in ≥4% of Patients in Placebo-Controlled Clinical Studies with Sapropterin Dihydrochloride MedDRA Preferred Term 20 mg/kg per day Sapropterin Dihydrochloride (N=74) Placebo (N=59) No. Patients (%) No. Patients (%) Headache 11 (15) 8 (14) Rhinorrhea 8 (11) 0 Pharyngolaryngeal pain 7 (10) 1 (2) Diarrhea 6 (8) 3 (5) Vomiting 6 (8) 4 (7) Cough 5 (7) 3 (5) Nasal congestion 3 (4) 0 In open-label, uncontrolled clinical trials (Studies 1 and 3) all patients received sapropterin dihydrochloride in doses of 5 to 20 mg/kg per day, and adverse reactions were similar in type and frequency to those reported in the double-blind, placebo-controlled clinical trials [see Clinical Studies (14) ]. In Study 5, 65 pediatric patients with PKU aged 1 month to 6 years received sapropterin dihydrochloride 20 mg/kg per day for 6 months. Adverse reactions in these patients were similar in frequency and type as those seen in other sapropterin dihydrochloride clinical trials except for an increased incidence of low Phe levels. Twenty-five percent (16 out of 65) of patients developed Phe levels below normal for age [see Warnings and Precautions (5.3) , Pediatric Use (8.4) , and Clinical Studies (14) ]. In Study 6, a long term, open-label, extension study of 111 patients aged 4 to 50 years, receiving sapropterin dihydrochloride in doses ranging from 5 to 20 mg/kg per day, adverse reactions were similar in type and frequency to those reported in the previous clinical studies. Fifty-five patients received sapropterin dihydrochloride both as dissolved and intact tablets. There were no notable differences in the incidence or severity of adverse reactions between the two methods of administration. The mean (± SD) exposure to sapropterin for the entire study population was 659 ± 221 days (maximum 953 days). In Study 7, 27 pediatric patients with PKU aged 0 to 4 years received sapropterin dihydrochloride 10 mg/kg per day or 20 mg/kg per day. Adverse reactions were similar in type and frequency to those observed in other clinical trials, with the addition of rhinitis, which was reported in 2 subjects (7.4%). Safety Experience from Clinical Studies for Non-PKU Indications Approximately 800 healthy subjects and patients with disorders other than PKU, some of whom had underlying neurologic disorders or cardiovascular disease, have been administered a different formulation of the same active ingredient (sapropterin) in approximately 19 controlled and uncontrolled clinical trials. In these clinical trials, subjects were administered sapropterin at doses ranging from 1 to 100 mg/kg per day for lengths of exposure from 1 day to 2 years. Serious and severe adverse reactions (regardless of causality) during sapropterin administration were seizures, exacerbation of seizures [see Warnings and Precautions (5.3) ] , dizziness, gastrointestinal bleeding, post-procedural bleeding, headache, irritability, myocardial infarction, overstimulation, and respiratory failure. Common adverse reactions were headache, peripheral edema, arthralgia, polyuria, agitation, dizziness, nausea, pharyngitis, abdominal pain, upper abdominal pain, and upper respiratory tract infection. 6.2 Postmarketing Experience The following adverse reactions have been reported during post-approval use of sapropterin dihydrochloride. 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. Hypersensitivity reactions including anaphylaxis and rash : Most hypersensitivity reactions occurred within several days of initiating treatment [see Warnings and Precautions (5.1) ]. Gastrointestinal reactions : esophagitis, gastritis, oropharyngeal pain, pharyngitis, esophageal pain, abdominal pain, dyspepsia, nausea, and vomiting [see Warnings and Precautions (5.2) ] . Hyperactivity : Two cases have been reported. In one case, the patient received an accidental overdosage of sapropterin dihydrochloride [see Warnings and Precautions (5.6) , Overdosage (10) ] .

Table 4 includes drugs with clinically important drug interactions when administered with sapropterin dihydrochloride and instructions for preventing or managing them. Table 4: Clinically Relevant Drug Interactions Levodopa Clinical Impact Sapropterin dihydrochloride may increase the availability of tyrosine, a precursor of levodopa. Neurologic events were reported post-marketing in patients receiving sapropterin and levodopa concomitantly for a non-PKU indication [see Warnings and Precautions (5.5) ] Intervention Monitor patients for a change in neurologic status. Inhibitors of Folate Synthesis (e.g., methotrexate, valproic acid, phenobarbital, trimethoprim) Clinical Impact In vitro and in vivo nonclinical data suggest that drugs that inhibit folate synthesis may decrease the bioavailability of endogenous BH4 by inhibiting the enzyme dihydrofolate reductase, which is involved in the recycling (regeneration) of BH4. This reduction in net BH4 levels may increase Phe levels. Intervention Consider monitoring blood Phe levels more frequently during concomitant administration. An increased dosage of sapropterin dihydrochloride may be necessary to achieve a biochemical response. Drugs Affecting Nitric Oxide-Mediated Vasorelaxation (e.g., PDE-5 inhibitors such as sildenafil, vardenafil, or tadalafil) Clinical Impact Both sapropterin dihydrochloride and PDE-5 inhibitors may induce vasorelaxation. A reduction in blood pressure could occur; however, the combined use of these medications has not been evaluated in humans. Intervention Monitor blood pressure. • Inhibitors of Folate Synthesis (e.g., methotrexate, valproic acid, phenobarbital, trimethoprim) : Can decrease endogenous BH4 levels; monitor blood Phe levels more frequently and adjust sapropterin dihydrochloride dosage as needed. ( 7 ) • Drugs Affecting Nitric Oxide-Mediated Vasorelaxation (e.g., PDE-5 inhibitors) : Potential for vasorelaxation; monitor blood pressure. ( 7 )