Spinal Muscular Atrophy

Spinal muscular atrophy destroys motor neurones from birth. Three therapies now exist, yet UK adults wait 25 years between diagnosis and treatment.
About Spinal Muscular Atrophy

In numbers

  • SMA affects an estimated 1 in 6,000 to 10,000 live births globally, with a carrier frequency of around 1 in 40 to 50 in European populations.
  • The UK’s prevalent SMA population is estimated at 668 to 1,336 patients, alongside an active Adult SMA REACH registry of around 420 adults.
  • SMA REACH UK’s paediatric registry of 507 children (2019 to 2024) recorded 42% Type 1, 37% Type 2 and 21% Type 3 cases.

Special details

  • England has not yet added SMA to its national newborn blood spot programme; an evaluation is under way, with full rollout expected by late 2025 or 2026.
  • The United States screens for SMA in more than 40 states, having added it to the Recommended Uniform Screening Panel in 2018.
  • Global lifetime prevalence has been modelled at around 1 in 10,000, rising to roughly 1 in 3,700 in high-income countries with stronger diagnostic ascertainment.
Signs and symptoms of Spinal Muscular Atrophy
In the UK adult cohort, mean age at diagnosis was 9.88 years but mean age at first treatment was 34.5 years, a 25-year gap driven by treatment availability, not diagnostic delay.
Profound hypotonia

Profound hypotonia

The floppy-infant sign present in almost all untreated Type 1 cases from birth or early infancy.

Absent deep tendon reflexes

Absent deep tendon reflexes

Near universal in untreated Type 1 disease, reflecting loss of anterior horn cells.

Minipolymyoclonus

Minipolymyoclonus

Fine tremor of outstretched hands, a characteristic finding in around 70% of Type 2 patients.

Progressive scoliosis

Progressive scoliosis

Affects more than 60% of Type 2 patients by adolescence as trunk muscles weaken.

Proximal limb weakness

Proximal limb weakness

Gowers sign and waddling gait mark ambulatory Type 3 onset after 18 months.

Key challenges from product development to launch

Strategy and Business

Strategy and Business

  • The wrong disease or indication selected for investment
  • Indications tackled in the wrong order due to shaky success estimates
  • R&D returns slipping below the cost of capital
Clinical Development

Clinical Development

  • Trials delayed by low patient recruitment
  • High screen-failure rates that raise trial cost
  • Mixed cohorts that make the signals difficult to detect
HEOR, Access & Value

HEOR, Access & Value

  • A value case that arrives too late or is underdeveloped
  • Eligible population under-counted, budget-impact case unsubstantiated
  • Approved by the regulator, delayed at HTA
Medical Affairs

Medical Affairs

  • Fragmented, differently-coded healthcare data
  • Diagnostic delay that is long and unequal
  • No shared evidence base across functions
Launch and Commercial

Launch and Commercial

  • Launch planned without a view of the number of findable patients
  • Targeting too broad a population slows early uptake
  • RWE started too late to build the case

How Volv Global Helps

The earliest pipeline decisions carry lasting consequences: the wrong indication chosen, indications pursued in the wrong order, or capital committed where expected returns already trail its cost. Mistakes made this early are expensive to correct later.

A launch planned without a view of findable patients is poorly resourced from day one. Targeting too broad a population slows early uptake, and real-world evidence gathered too late leaves little time to build a strong access dossier.

Case Studies about Neuromuscular diseases

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