FDA approves Ionis's ZANVASTRO for Alexander disease

The U.S. Food and Drug Administration approved ZANVASTRO (zilganersen) on September 3, 2026 for the treatment of Alexander disease in pediatric and adult patients, Ionis Pharmaceuticals announced. ZANVASTRO is the first and only disease modifying treatment for AxD, an ultra-rare, progressive and often fatal neurological disorder that can affect motor, cognitive, autonomic and gastrointestinal function.¹

The drug is an RNA-targeted medicine designed to address the underlying disease mechanism of AxD by reducing production of glial fibrillary acidic protein, and is administered as a 50 mg quarterly intrathecal injection.¹

The approval rests on a pivotal study. In individuals 5 years of age and older, ZANVASTRO 50 mg demonstrated statistically significant and clinically meaningful stabilization of gait speed as assessed by the 10-Meter Walk Test compared to control at Week 61, with a least square mean difference of 33.3% and p=0.041.¹ The drug also showed improvement in gross motor function in patients 2 to 4 years old, as measured by the Gross Motor Function Measure-88, compared to control at Week 61.¹

On safety, ZANVASTRO showed a favorable safety and tolerability profile, with most adverse events mild or moderate, and serious treatment-emergent adverse events occurring less frequently than in the control group.¹ Labeling warns of aseptic meningitis risk; adverse reactions of aseptic meningitis were reported during the double-blind and open-label periods of the study, including one serious case that recurred in the open-label extension and required dose interruption and dexamethasone pretreatment.¹

With the approval, the FDA granted Ionis a Rare Pediatric Disease Priority Review Voucher, intended to accelerate regulatory review timelines for future applications.¹ ZANVASTRO will be available in the U.S. in the coming weeks.¹

In June 2026, Ionis licensed exclusive rights to develop and commercialize zilganersen outside the U.S. to Recordati, with regulatory submissions in Europe and Japan expected in 2027.¹