FDA Approves First Treatment for Alexander Disease

The FDA approved zilganersen (Zanvastro, Ionis Pharmaceuticals) for Alexander disease in pediatric and adult patients, establishing the first approved treatment for the rare progressive neurologic disorder.

Alexander disease is caused by mutations affecting glial fibrillary acidic protein (GFAP). Abnormal GFAP accumulates in supportive cells in the brain and progressively damages the nervous system. Clinical manifestations can include seizures, developmental regression, gait impairment, weakness, and increased intracranial pressure. Until this approval, management was limited to supportive care.

Zilganersen is an antisense oligonucleotide designed to reduce production of abnormal GFAP. It is administered as an injection into the spinal canal every 3 months.

The FDA based the approval on a multicenter randomized controlled study involving 49 patients aged 2 years or older and an open-label substudy involving 4 patients younger than 2 years.

Among patients aged 5 years or older with measurable gait impairment, treatment produced significantly better walking speed at 61 weeks than no treatment. Children aged 2 to 4 years improved on a broader motor assessment while control participants declined. For children younger than 2 years, the agency considered pharmacokinetic modeling and safety observations alongside the limited direct trial data.

Common adverse effects included vomiting, back pain, cough, headache, and post-lumbar puncture syndrome. Aseptic meningitis has also been reported. The FDA granted the therapy multiple expedited and rare-disease designations.

Source: U.S. Food and Drug Administration. FDA approves first drug to treat Alexander disease. News release. U.S. Food and Drug Administration; September 3, 2026. Accessed September 4, 2026.