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Backgrounders

Facts about spinal muscular atrophy
  • Individuals born with SMA do not make enough survival motor-neuron protein, which is key to motor development. Spinraza (nusinersen) is injected into the spinal fluid and boosts protein development.
  • SMA patients may require Spinraza treatment for the duration of their lives depending on the patient’s response. The dosing schedule is six doses in the first year and three doses in subsequent years. Each drug injection is usually given in a hospital setting.
  • While SMA primarily affects infants, it can also affect older children and adults. The disease first manifests in various ways, depending on age of onset. Infants present with severe hypotonia and feeding difficulties, while later onset in young children may appear as difficulty with stairs and frequent falls. Adult onset SMA presents as mild proximal muscle weakness.
    • Approximately 60% of the diagnosed cases will have signs and symptoms showing by the age of six months. SMA presenting by the age of six months is the most common genetic cause of infant mortality. These patients typically have a life expectancy of two years.
    • Patients who show signs and symptoms between seven months and 18 months of age usually are unable to walk independently, have delayed motor milestones, respiratory issues and the possibility of a shortened life expectancy.
    • Patients with onset from 18 months to 18 years of age represent roughly 10% to 20% of all diagnosed cases. They experience muscle weakness but are expected to have a normal life expectancy.
  • Approximately one in 40 people carry the SMA gene. If both parents are carriers, there is a one-in-four probability that the SMA gene will be passed to children.
  • The list cost of Spinraza, as set by its manufacturer, Biogen, is substantial at approximately $708,000 per patient for the first year, and roughly $354,000 every year following.