The U.S. Food and Drug Administration (FDA) has approved Zanvastro (zilganersen) injection for the treatment of Alexander disease in pediatric and adult patients, marking the first FDA-approved therapy for this rare and progressive neurological disorder.
Alexander disease is a rare neurological condition caused by mutations in the gene responsible for producing glial fibrillary acidic protein (GFAP). The abnormal GFAP protein can accumulate in the brain’s supportive cells, progressively damaging the nervous system. The disease affects fewer than one in a million people and may result in seizures, loss of developmental milestones, difficulty walking, muscle weakness and increased pressure in the brain.
Zanvastro is an antisense oligonucleotide designed to address the underlying mechanism of Alexander disease. The therapy reduces production of abnormal GFAP protein before it can accumulate and contribute to further neurological damage. It is administered by injection into the spinal canal every three months by a trained healthcare professional.
The FDA evaluated Zanvastro in a multicenter, randomized, controlled clinical study involving 49 pediatric and adult patients aged two years and older, along with an open-label substudy involving four patients younger than two years. Because of the rarity of Alexander disease and its broad age range, the FDA considered evidence supporting treatment from infancy through adulthood.
In patients aged five years and older who had measurable walking difficulties at the start of the study, those receiving Zanvastro demonstrated significantly better walking speed at 61 weeks compared with patients who did not receive treatment. For children aged two to four years, researchers used a broader motor assessment covering abilities such as standing, walking, running and jumping. Children treated with Zanvastro improved on this measure, while the control group declined.
Evidence in patients younger than two years was more limited because of the extremely small patient population and the absence of a concurrent control group. The FDA said pharmacokinetic modeling indicated that drug exposure in this age group was expected to be comparable with older children receiving the same dose. Safety information from four treated infants, together with data from older pediatric patients, supported extending the indication to the youngest patients.
The most commonly reported adverse effects associated with Zanvastro include vomiting, back pain, cough, headache and post-lumbar puncture syndrome. Aseptic meningitis has also been reported, and patients and caregivers are advised to contact healthcare professionals if symptoms suggestive of meningitis develop.
Zanvastro received several FDA development designations, including Orphan Drug, Fast Track, Breakthrough Therapy and Rare Pediatric Disease designations. The approval was granted to Ionis Pharmaceuticals, Inc.
The approval represents a significant development in rare neurological disease treatment because Zanvastro is not simply intended to manage symptoms; it directly targets the abnormal GFAP protein production associated with Alexander disease.
