The U.S. Food and Drug Administration has approved Zanvastro (zilganersen) injection for the treatment of Alexander disease in pediatric and adult patients, marking the first approved therapy for the rare neurological condition.

Zanvastro, developed by Ionis Pharmaceuticals, is an antisense oligonucleotide that works by reducing production of abnormal glial fibrillary acidic protein (GFAP) before it accumulates and causes nerve damage. It is administered as an injection into the spinal canal every three months by a trained healthcare professional.

Alexander disease is a rare progressive neurological disorder affecting fewer than 1 in a million people, caused by mutations in the gene that produces GFAP. Symptoms can include seizures, loss of developmental milestones, difficulty walking, muscle weakness, and increased brain pressure.

The FDA evaluated efficacy and safety in a multicenter, randomized, controlled clinical study enrolling 49 pediatric and adult patients aged 2 years and older, and a separate open-label substudy of 4 patients under 2 years of age. In patients aged 5 and older with measurable walking difficulties, those treated with Zanvastro showed significantly better walking speed at 61 weeks compared to untreated patients. In children aged 2 to 4, those receiving the drug showed motor skill improvement while the control group declined.

The most common side effects include vomiting, back pain, cough, headache, and post-lumbar puncture syndrome. Aseptic meningitis has also been reported in treated patients.

Zanvastro received Orphan Drug, Fast Track, Breakthrough Therapy, Rare Pediatric Disease, and Priority Review Voucher designations from the FDA.