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Spinal Muscular Atrophy Gene Therapy

AAV9-Based SMN1 Replacement

Written by: Saygı Hospital Health Guide Editorial Board
Last updated:

This content has been compiled by the Saygı Hospital Health Guide Editorial Board and is periodically reviewed by a specialist physician.

References (5)

This content is for informational purposes only and does not constitute medical advice. You can book an appointment at our Nöroloji department. Book Appointment →

What is Spinal Muscular Atrophy Gene Therapy?

AAV9 vector carrying functional SMN1 cDNA, delivered as one-time IV infusion.

AAV9 crosses blood-brain barrier and transduces motor neurons in spinal cord.

Replaces missing or non-functional SMN1 gene in patients with SMA type 1, 2, 3.

Approved by FDA for pediatric SMA <2 years of age (some regulatory variations).

Symptoms

SMA type 1 (Werdnig-Hoffmann): hypotonia, weakness, respiratory failure within 6 months; without treatment, death by age 2.
SMA type 2: onset 6-18 months, never walk independently.
SMA type 3: later onset (>18 months), walk but progressive weakness.
SMA type 4: adult onset, mild weakness.

Risk Factors

Genetic: homozygous SMN1 deletion or biallelic SMN1 mutations.
SMN2 copy number affects severity (more copies, milder).
Age at treatment critical (earlier = better outcome).
Anti-AAV9 antibody titers must be low (<1:50) for eligibility.
Pre-treatment motor neuron loss may limit response.

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • Newborn with SMA detected on screening.
  • Hypotonic infant with weak cry, poor feeding.
  • Confirmed genetic diagnosis (SMN1 deletion).
  • Family history of SMA in older sibling.
  • Consider genetic testing in unexplained infantile hypotonia.

Treatment Methods

01
Single IV infusion of onasemnogene abeparvovec (1.1 × 10¹⁴ vg/kg) over 60 minutes.
02
Pre-screening: anti-AAV9 antibody titer, baseline LFTs, troponin, platelets.
03
Pre-treatment prednisolone 1 mg/kg/day starting 24 hours before infusion, continuing for at least 30 days then taper.
04
Adverse effects: hepatotoxicity (transaminase elevation, requires close monitoring), thrombocytopenia, troponin elevation, thrombotic microangiopathy (rare, severe).
05
Concurrent supportive care: respiratory (BiPAP, cough assist), nutrition (G-tube if needed), physical therapy, orthopedics.
06
May combine with nusinersen or risdiplam for additional benefit (sequential or combination — investigational).
07
Cost: extremely high (~$2.1M USD); coverage varies by country.
08
Long-term durability data emerging; functional improvements maintained at 5+ years.
09
Newborn screening for SMA now standard in many countries — earlier diagnosis enables presymptomatic treatment with best outcomes.

Which Department to Visit?

You can visit our Nöroloji department for these complaints. Our specialist physicians will create the most suitable treatment plan for you.

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Health Disclaimer: The information on this page is prepared for general informational purposes only. It does not replace medical diagnosis and treatment. Please consult your physician for your complaints. Saygı Hospital does not accept responsibility for actions taken based on the information on this page.