| Sumario: | Nitisinone (Orfadin) is indicated for the treatment of patients with hereditary tyrosinemia type 1 (HT- 1) in combination with dietary restriction of tyrosine and phenylalanine. Nitisinone is available as 2 mg, 5 mg, 10 mg, and 20 mg capsules for oral administration. The submitted price of nitisinone is based on dose: 2 mg ($22.50), 5 mg ($53.30), 10 mg ($100), and 20 mg ($193.33). The recommended initial dosage in pediatric and adult populations is 1 mg/kg body weight daily divided in two doses administered orally. If plasma or urine succinylacetone is still detectable one month after starting treatment, the dosage should be increased to 1.5 mg/kg daily to a maximum dosage of 2 mg/kg daily. If the biochemical response is satisfactory, dosage should be adjusted only according to body weight gain. Although nitisinone can be used in both pediatric and adult populations, the manufacturer's economic evaluation is based on a subset of the labelled indication: the treatment of newborns who are identified and treated within one month of birth, either through a newborn screening program or through physical examination, patient history, and specialized tests (including urine succinylacetone levels). The submitted cost-utility analysis compares costs and health benefits associated with nitisinone 1 mg/kg plus best supportive care (BSC; dietary restriction) versus BSC (dietary restriction) alone in the treatment of newborns at least one month old, from a health ministry perspective. The model is based on three health states: diagnosed with HT-1; liver transplant with associated tunnel states; and dead. The time horizon was a patient's lifetime (100 years), and future costs and benefits were discounted at 1.5% annually. Comparative treatment effect was based on assumptions regarding premature mortality taken from a study of a Quebec-based cohort (Larochelle et al.) of newborns followed for up to 14 years. Utility values were derived from a cohort of men (average age 54 years) with decompensated cirrhosis resulting from chronic hepatitis B infection and measured with the Health Utility Index Mark 3 (HUI3) instrument. Assumptions regarding resource use and costs were derived from a Quebec-based study of HT-1 patients as well as a British Columbia-based study of liver transplantation costs.
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