FDA Approval

FDA Approves Zanvastro as First Treatment for Alexander Disease

Edited by:
Anthony Calabro, MA

Key Highlights

  • Zilganersen is the first FDA-approved treatment for Alexander disease.
  • Patients aged 5 years or older demonstrated better walking speed at 61 weeks than untreated patients.
  • Treated children aged 2 to 4 years improved on a broader motor assessment while control patients declined.
  • Treatment is administered into the spinal canal every 3 months.

On September 3, the FDA approved Zanvastro (zilganersen) injection for pediatric and adult patients with Alexander disease. Zilganersen is an antisense oligonucleotide that reduces production of abnormal glial fibrillary acidic protein (GFAP) before it can accumulate. It is the first approved treatment for the disease and the first to target its underlying protein accumulation. Zilganersen is injected into the spinal canal every 3 months by a trained healthcare professional.

Alexander disease is a rare, progressive neurologic disorder caused by mutations in the gene responsible for producing GFAP. Abnormal GFAP accumulates in the brain’s supportive cells and progressively damages the nervous system. The disease affects fewer than 1 in 1 million people and may cause serious or life-threatening manifestations, including seizures, loss of developmental milestones, difficulty walking, muscle weakness, and increased intracranial pressure.

Efficacy and safety were evaluated in a multicenter, randomized, controlled study (NCT04849741) that enrolled 49 patients aged 2 years or older and an open-label substudy involving 4 children younger than 2 years. Among patients aged 5 years or older who had measurable walking difficulties at baseline, those receiving zilganersen had significantly better walking speed at 61 weeks than untreated patients. Treated children aged 2 to 4 years improved on an assessment covering standing, walking, running, and jumping, whereas the control group declined. For children younger than 2 years, pharmacokinetic modeling indicated expected drug exposure similar to that in older children receiving the same dose.

“Today’s approval is a landmark moment for this community, offering the first therapy that addresses the underlying cause of this rare and serious disease,” Emily Freilich, MD, director of the FDA Division of Neurology I, said in a press release.

The most common adverse effects were vomiting, back pain, cough, headache, and post–lumbar puncture syndrome. Aseptic meningitis has also been reported; patients and caregivers should notify clinicians if symptoms consistent with meningitis develop.

Reference
US Food and Drug Administration. FDA approves first drug to treat Alexander disease. Published September 3, 2026. Accessed September 15, 2026. https://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-treat-alexander-disease