The US Food and Drug Administration (FDA) has approved Zanvastro (zilganersen) injection for the treatment of Alexander disease in paediatric and adult patients.
Developed by Ionis Pharmaceuticals, Zanvastro is the first FDA-approved treatment for Alexander disease and the first therapy to directly target the protein buildup that drives the disease.
Alexander disease is an ultra-rare, progressive and often fatal neurological disorder that can affect motor, cognitive, autonomic and gastrointestinal function. Until now, treatment has primarily focused on managing symptoms and providing supportive care.
“For patients with Alexander disease and their families, there have been no approved treatment options — only supportive care while the disease progresses,” said Emily Freilich, Director of the Division of Neurology I in the FDA’s Center for Drug Evaluation and Research.
She described the approval as a landmark moment for the Alexander disease community, offering the first therapy that addresses the underlying cause of the disease.
Brett P. Monia, CEO of Ionis, said the approval marks the company’s first independent launch from its neurology pipeline and highlights the potential of its RNA-targeted technology to address serious neurological diseases with limited treatment options.
Amy Waldman, paediatric neurologist and lead investigator for the Zanvastro study at Children’s Hospital of Philadelphia, said the treatment could allow clinicians to move beyond managing individual manifestations of the disease and address its underlying biology, with the potential to improve outcomes for patients.
Know more about Alexander disease
Alexander disease is caused by mutations in the gene that produces glial fibrillary acidic protein (GFAP). When the protein is abnormal, it accumulates in the brain’s supportive cells, damaging the nervous system over time. The disease affects fewer than one in a million people worldwide.
The condition can cause a range of serious and potentially life-threatening problems, including seizures, loss of developmental milestones, difficulty walking, muscle weakness and increased pressure in the brain.
Zanvastro is an antisense oligonucleotide — a type of medicine designed to reduce the production of the abnormal GFAP protein before it can accumulate and cause further damage. It is administered once every three months as an injection into the spinal canal by a trained healthcare professional.
The FDA approval was supported by positive results from a pivotal study of Zanvastro in people living with Alexander disease. Among patients aged five years and older, those treated with Zanvastro 50 mg demonstrated statistically significant and clinically meaningful stabilisation of gait speed at Week 61 compared with untreated patients.
Zanvastro also demonstrated improvement in gross motor function among patients aged two to four years compared with the control group at Week 61.
For patients younger than two years, direct clinical trial data were limited because of the rarity of the disease and the lack of a concurrent control group. Pharmacokinetic modelling indicated that drug exposure in this age group was expected to be similar to that observed in older children receiving the same dose. This was supported by safety data from four patients younger than two years who were treated in the study, as well as safety data from older paediatric patients.
The FDA said this approach supported extending the indication to the youngest patients while maintaining the evidentiary standards required for approval.
With the approval of Zanvastro, the FDA also granted Ionis a Rare Paediatric Disease Priority Review Voucher (PRV), a programme designed to incentivise the development of therapies for serious or life-threatening rare paediatric diseases by providing a mechanism that can potentially accelerate regulatory review of a subsequent application.
Ionis said Zanvastro will be available in the US in the coming weeks.
In June 2026, Ionis entered into a licensing agreement with Recordati, an Italy-headquartered pharmaceutical company focused on speciality and rare diseases. Under the agreement, Recordati obtained exclusive rights to develop and commercialise zilganersen outside the US.
Ionis is working with Recordati to prepare regulatory submissions in Europe and Japan, which are expected in 2027.
