| Sumario: | Spinal muscular atrophy (SMA) is a severe neuromuscular disease and is the leading genetic cause of infant death. It is characterized by the degeneration of alpha motor neurons in the anterior horn of the spinal cord, leading to progressive muscle weakness. The most common form of SMA, 5q SMA, makes up over 95% of all cases and is an autosomal recessive disorder caused by homozygous deletion or deletion and mutation of the alleles of the survival motor neuron 1 (SMN1) gene. SMA is a rare disease and estimates of its incidence and prevalence vary between studies. The incidence of SMA is often cited as being approximately 10 in 100,000 live births. Four clinical subtypes of SMA are described; SMA type I makes about 60% of SMA diagnoses where patients show symptoms before 6 months of age, never achieve the motor milestone of sitting unsupported, and generally do not survive past two years of age due to respiratory failure; SMA type II achieve the milestone of sitting unsupported, but never walk independently. Symptoms generally appear between 6 to 18 months after birth and most patients will survive past the age of 25, with life expectancy improved by aggressive supportive care; SMA type III makes up about 10% to 20% of SMA cases3 and presents between 18 months of age and adulthood. These patients are able to walk independently at some point in their life and typically have a normal life expectancy; SMA type IV constitutes very small proportion of SMA cases, has an adult onset SMA, and is the mildest form of the disease. Although muscle weakness is present, these patients retain the ability to walk, have a normal life expectancy, and do not suffer from respiratory or nutritional issues. Nusinersen (Spinraza) is a solution for intrathecal injection, indicated for the treatment of 5q spinal muscular atrophy (SMA). It is available as a single use solution in a 5mL vial size (12 mg) administered intrathecal by lumbar puncture. The recommended dose is: initial treatment with 4 loading doses, with the first 3 loading doses administered at 14-day intervals (day 0, day 14, and day 28), and a final loading dose approximately 30 days after the third loading dose (day 63); maintenance treatment is 12 mg every 4 months. The marketed price of $118,000 per 5mL vial, the annual cost of treatment with nusinersen ranges from $354,000 for maintenance treatment (3 doses) to 08,000 in the 1st year (6 doses). The manufacturer's listing request is as per the Health Canada indication. The manufacturer submitted three cost-utility analyses for SMA type I, II and II. Each analysis was based on a Markov state-transition model comparing nusinersen with current standard of care (or real world care [RWC] which includes supportive symptomatic treatment of respiratory, nutritional, and orthopedic function decline) - for patients with q5 SMA.
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