FDA approves the first drug for Alexander disease

The US Food and Drug Administration approved Zanvastro (zilganersen) on 3 September 2026, the first treatment for Alexander disease. Ionis Pharmaceuticals developed the drug as an antisense oligonucleotide that reduces production of glial fibrillary acidic protein, the protein whose accumulation drives nerve damage in the disease. It is given as an intrathecal injection every three months, and the label covers pediatric and adult patients, from infants through adulthood.

The approval rests on trial NCT04849741, a multicentre randomised controlled study of 49 patients aged two and older, with an open-label substudy of four children under two. Among participants aged five and over who had difficulty walking at baseline, walking speed at week 61 was significantly better than in the control group. Children aged two to four gained motor skills — standing, walking, running, jumping — while controls declined.

Alexander disease is a leukodystrophy, and until now it had no disease-modifying therapy at all. The FDA lists vomiting, back pain, cough, headache and post-lumbar-puncture syndrome among common side effects, and notes that aseptic meningitis has been reported, with instructions to report meningitis-like symptoms immediately.