On September 3, 2026, the U.S. Food and Drug Administration (FDA) approved Zanvastro (zilganersen) injection for the treatment of Alexander disease in pediatric and adult patients. It is the first FDA-approved treatment for this rare and serious disease, and the first therapy to directly target the protein buildup that drives it.
A Breakthrough for a Rare Neurological Disease
Alexander disease is a rare, progressive neurological disorder caused by mutations in the gene that produces glial fibrillary acidic protein (GFAP). When this protein is abnormal, it accumulates in the brain’s supportive cells and damages the nervous system over time. The disease affects fewer than 1 in a million people and can cause serious, potentially life-threatening problems, including seizures, loss of developmental milestones, difficulty walking, muscle weakness and increased pressure in the brain.
Until now, there were no approved treatment options, only supportive care while the disease progressed. Zanvastro, granted to Ionis Pharmaceuticals, is an antisense oligonucleotide, a type of medicine that reduces the production of abnormal GFAP before it can accumulate and cause further damage. It is given as an injection into the spinal canal every three months by a trained healthcare professional.
FDA’s Statement
Emily Freilich, M.D., Director of the Division of Neurology I in the FDA’s Center for Drug Evaluation and Research, said: “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.”
Clinical Trial Results
The efficacy and safety of Zanvastro were evaluated in a multicenter, randomized, controlled clinical study (NCT04849741) enrolling 49 pediatric and adult patients aged 2 years and older, and in an open-label substudy of 4 patients under 2 years of age. Key findings:
- In patients aged 5 years and older who had measurable difficulties with walking at baseline, those treated with Zanvastro showed significantly better walking speed at 61 weeks compared with those who received no treatment.
- In children aged 2 to 4 years, a broader assessment of motor skills (standing, walking, running and jumping) was used. Children treated with Zanvastro improved on this measure, while those in the control group declined.
For patients under 2 years of age, direct clinical trial data were limited by the rarity of the disease and the lack of a concurrent control. Pharmacokinetic modeling indicated that drug levels in this age group are expected to be similar to those in older children at the same dose, and safety data from four patients under 2 years supported extending the indication to the youngest patients.
Safety and Possible Side Effects
The most common side effects of Zanvastro are:
- Vomiting
- Back pain
- Cough
- Headache
- Post-lumbar puncture syndrome
Aseptic meningitis has been reported in patients treated with Zanvastro. Patients and caregivers should inform their healthcare provider if symptoms consistent with meningitis develop, and should carefully review the full prescribing information when making treatment decisions.
Regulatory Designations
Zanvastro received Orphan Drug, Fast Track, Breakthrough Therapy, and Rare Pediatric Disease and Priority Review Voucher designations, reflecting the serious and rare nature of Alexander disease.
What This Means for Patients
The approval marks an important step for families affected by Alexander disease, a condition with no previously approved treatment. Patients and physicians outside the United States who are looking for information on access to newly approved rare disease medicines can contact Indian Pharma Network for guidance under the Named Patient Program.
