2.1 Dosage

2.2 Preparation and Administration Instructions

5.1 Elevated Plasma Tyrosine Levels, Ocular Symptoms, Developmental Delay and Hyperkeratotic Plaques

Nitisinone is an inhibitor of 4-hydroxyphenyl-pyruvate dioxygenase, an enzyme in the tyrosine metabolic pathway [see Clinical Pharmacology (12.1)]. Therefore, treatment with ORFADIN may cause an increase in plasma tyrosine levels in patients with HT-1. Maintain concomitant reduction in dietary tyrosine and phenylalanine while on ORFADIN treatment. Do not adjust ORFADIN dosage in order to lower the plasma tyrosine concentration. Maintain plasma tyrosine levels below 500 micromol/L. Inadequate restriction of tyrosine and phenylalanine intake can lead to elevations in plasma tyrosine levels and levels greater than 500 micromol/L may lead to the following:

• Ocular signs and symptoms including corneal ulcers, corneal opacities, keratitis, conjunctivitis, eye pain, and photophobia have been reported in patients treated with ORFADIN [see Adverse Reactions (6.1)]. In a clinical study in a non HT-1 population without dietary restriction and reported tyrosine levels >500 micromol/l both symptomatic and asymptomatic keratopathies have been observed. Therefore, perform a baseline ophthalmologic examination including slit-lamp examination prior to initiating ORFADIN treatment and regularly thereafter. Patients who develop photophobia, eye pain, or signs of inflammation such as redness, swelling, or burning of the eyes or tyrosine levels are > 500 micromol/L during treatment with ORFADIN should undergo slit-lamp reexamination and immediate measurement of the plasma tyrosine concentration.
• Variable degrees of intellectual disability and developmental delay. In patients treated with ORFADIN who exhibit an abrupt change in neurologic status, perform a clinical laboratory assessment including plasma tyrosine levels.
• Painful hyperkeratotic plaques on the soles and palms

In patients with HT-1 treated with dietary restrictions and ORFADIN who develop elevated plasma tyrosine levels, assess dietary tyrosine and phenylalanine intake.

5.2 Leukopenia and Severe Thrombocytopenia

In clinical trials, patients treated with ORFADIN and dietary restriction developed transient leukopenia (3%), thrombocytopenia (3%), or both (1.5%) [see Adverse Reactions (6.1)]. No patients developed infections or bleeding as a result of the episodes of leukopenia and thrombocytopenia. Monitor platelet and white blood cell counts during ORFADIN therapy.

5.3 Risk of Adverse Reactions Due to Glycerol Content of ORFADIN Oral Suspension

Oral doses of glycerol of 10 grams or more have been reported to cause headache, upset stomach and diarrhea. ORFADIN oral suspension contains 500 mg/mL of glycerol. Patients receiving more than 20 mL of ORFADIN oral suspension (10 grams glycerol) as a single dose are at increased risk of these adverse reactions. Consider switching patients who are unable to tolerate the oral suspension to ORFADIN 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 clinical practice.

ORFADIN was studied in one open-label, uncontrolled study of 207 patients with HT-1, ages 0 to 22 years at enrollment (median age 9 months), who were diagnosed with HT-1 by the presence of succinylacetone in the urine or plasma. The starting dose of ORFADIN was 0.3 to 0.5 mg/kg twice daily, and the dose was increased in some patients to 1 mg/kg twice daily based on weight, biochemical, and enzyme markers. The recommended starting dosage of ORFADIN is 0.5 mg/kg twice daily [see Dosage and Administration (2.1)]. Median duration of treatment was 22 months (range 0.1 to 80 months).

The most serious adverse reactions reported during ORFADIN treatment were thrombocytopenia, leukopenia, porphyria, and ocular/visual complaints associated with elevated tyrosine levels [see Warnings and Precautions (5.1, 5.2)]. Fourteen patients experienced ocular/visual events. The duration of the symptoms varied from 5 days to 2 years. Six patients had thrombocytopenia, three of which had platelet counts 30,000/microL or lower. In 4 patients with thrombocytopenia, platelet counts gradually returned to normal (duration up to 47 days) without change in ORFADIN dose. No patients developed infections or bleeding as a result of the episodes of leukopenia and thrombocytopenia.

Patients with HT- 1 are at increased risk of developing porphyric crises, hepatic neoplasms, and liver failure requiring liver transplantation. These complications of HT-1 were observed in patients treated with nitisinone for a median of 22 months during the clinical trial (liver transplantation 13%, liver failure 7%, malignant hepatic neoplasms 5%, benign hepatic neoplasms 3%, porphyria 1%).

The most common adverse reactions reported in the clinical trial are summarized in Table 1.

Adverse reactions reported in less than 1% of the patients, included death, seizure, brain tumor, encephalopathy, hyperkinesia, cyanosis, abdominal pain, diarrhea, enanthema, gastrointestinal hemorrhage, melena, elevated hepatic enzymes, liver enlargement, hypoglycemia, septicemia, and bronchitis.

8.1 Pregnancy

8.2 Lactation

8.4 Pediatric Use

The safety and effectiveness of ORFADIN have been established in pediatric patients for the treatment of HT-1 in combination with dietary restriction of tyrosine and phenylalanine. Use of ORFADIN in pediatric patients is supported by evidence from one open-label, uncontrolled clinical study conducted in 207 patients with HT-1 ages 0 to 22 years (median age 9 months) [see Clinical Studies (14)].

8.5 Geriatric Use

Clinical studies of nitisinone did not include any subjects aged 65 and over. No pharmacokinetic studies of nitisinone have been performed in geriatric patients. In general, dose selection for an elderly patient should be cautious reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and concomitant disease or other drug therapy in this patient population.

12.1 Mechanism of Action

Nitisinone is a competitive inhibitor of 4-hydroxyphenyl-pyruvate dioxygenase, an enzyme upstream of fumarylacetoacetate hydrolase (FAH) in the tyrosine catabolic pathway. By inhibiting the normal catabolism of tyrosine in patients with HT-1, nitisinone prevents the accumulation of the catabolic intermediates maleylacetoacetate and fumarylacetoacetate. In patients with HT-1, these catabolic intermediates are converted to the toxic metabolites succinylacetone and succinylacetoacetate, which are responsible for the observed liver and kidney toxicity. Succinylacetone can also inhibit the porphyrin synthesis pathway leading to the accumulation of 5-aminolevulinate, a neurotoxin responsible for the porphyric crises characteristic of HT-1.

12.2 Pharmacodynamics

In a clinical study, patients with HT-1 were diagnosed by the presence of succinylacetone in urine or plasma and treated with ORFADIN [see Clinical Studies (14)]. In all 186 patients whose urine succinylacetone was measured, the urinary succinylacetone concentration decreased to less than 1 mmol/mol creatinine, the lower limit of quantitation. The median time to normalization of urine succinylacetone was 0.3 months. The probability of recurrence of abnormal values of urine succinylacetone was 1% at a nitisinone concentration of 37 micromol/L (95% confidence interval: 23, 51 micromol/L). In 87% (150/172) of patients whose plasma succinylacetone was measured, the plasma succinylacetone concentration decreased to less than 0.1 micromol/L, the lower limit of quantitation. The median time to normalization of plasma succinylacetone was 3.9 months.

In another study, comparing two dosing regimens, succinylacetone was measured in urine and/or blood in 16 patients with HT-1 aged 5 years to 24 years. All study patients were on a stable ORFADIN daily dosage (0.4 mg/kg/day to 1 mg/kg/day) during both study dosing regimens. After at least 4 weeks of twice daily dosing with ORFADIN, both the urine and/or blood succinylacetone concentrations were below the limit of quantitation for the assay. Patients were then switched to once daily dosing with the same total daily dosage of ORFADIN and blood and/or urine succinylacetone concentrations remained undetectable when measured following at least 4 weeks of treatment with once daily dosing.

Nitisinone inhibits catabolism of the amino acid tyrosine and can result in elevated plasma levels of tyrosine. Therefore, treatment with nitisinone requires restriction of the dietary intake of tyrosine and phenylalanine to prevent the toxicity associated with elevated plasma levels of tyrosine [see Warnings and Precautions (5.1)].

12.3 Pharmacokinetics

The single-dose pharmacokinetics of nitisinone have been studied for both ORFADIN capsules and ORFADIN oral suspension in healthy adult subjects and the multiple-dose pharmacokinetics have been studied for ORFADIN capsules in healthy subjects.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

The carcinogenic potential of nitisinone was assessed in a 26-week oral (gavage) carcinogenicity study in Tg.rasH2 mice. There were no drug-related neoplastic findings in male or female Tg.rasH2 mice at doses up to 100 mg/kg/ day nitisinone (approximately 8.1 times the recommended initial dose of 1 mg/kg/day on a body surface area basis).

Nitisinone was not genotoxic in the Ames test and the in vivo mouse liver unscheduled DNA synthesis (UDS) test. Nitisinone was mutagenic in the mouse lymphoma cell (L5178Y/TK+/-) forward mutation test and in an in vivo mouse bone marrow micronucleus test.

In a single dose-group study in rats given 100 mg/kg (16.2 times the recommended initial dose of 1 mg/kg/day on a body surface area basis), reduced litter size, decreased pup weight at birth, and decreased survival of pups after birth was demonstrated.

Preparation and Administration Instructions [see Dosage and Administration (2.2)]

Preparing a Bottle Without the Adapter Already Inserted:

• Store the bottle in the refrigerator prior to first use.
• Remove the bottle from the refrigerator. Calculate 60 days from when the bottle is removed from the refrigerator. Write this date as the “Discard after” date on the bottle label.
• Allow the bottle to warm to room temperature (30 to 60 minutes).
• Shake the bottle vigorously for at least 20 seconds until the solid cake at the bottom of the bottle is completely dispersed. Check that there are no particles left at the bottom of the bottle. Foam will form in the bottle.
• Insert the bottle adapter.

Preparing a Bottle With the Adapter Inserted:

• Shake the bottle vigorously for at least 5 seconds. Check that there are no particles left at the bottom of the bottle. Foam will form in the bottle.

Measuring and Administering the Dose

Once the bottle is prepared with the adapter:

1. Use the oral syringe to measure the dose.
2. Keep the bottle upright and insert the oral syringe into the adapter.
3. Carefully turn the bottle upside down with the oral syringe in place. Wait for the foam to rise to the top of the bottle.
4. Pull back on the syringe plunger to withdraw the dose.
5. Leave the syringe in the adapter and turn the bottle upright.
6. Remove the syringe from the adapter by gently twisting it out of the bottle.
7. Dispense the dose into the patient's mouth.
8. Do not remove the bottle adapter.
9. Store the bottle at room temperature (not above 25°C).

Elevated Plasma Tyrosine Levels, Ocular Symptoms, Developmental Delay and Hyperkeratotic Plaques

• Inform patients that inadequate restriction may be associated with ocular signs and symptoms, intellectual disability and developmental delay, and painful hyperkeratotic plaques on the soles and palms. Advise patients and caregivers of the need to maintain dietary restriction of tyrosine and phenylalanine and to report any unexplained ocular, neurologic, or other symptoms promptly to their healthcare provider [see Warnings and Precautions (5.1)].

Risk of Adverse Reactions Due to Glycerol Content of ORFADIN Oral Suspension

Advise patients receiving doses of greater than 20 mL of ORFADIN oral suspension that they may experience headache, upset stomach and diarrhea due to the glycerol component of the formulation and if they develop symptoms to report these to their healthcare provider [see Warnings and Precautions (5.3)].

Manufactured by:
Apotek Produktion & Laboratorier AB, Sweden

Marketed by:
Sobi, Inc

890 Winter Street
Waltham, MA 02451