– New data highlight potential treatment benefit across multiple AxD symptom domains, reinforcing zilganersen's positive impact on people living with this rare, often fatal neurological disease –

– PDUFA date set for September 22, 2026 –

Ionis Pharmaceuticals, Inc. (NASDAQ:IONS) today announced additional positive results from the pivotal study of zilganersen in children and adults living with Alexander disease (AxD), a rare, progressive and often fatal neurological condition with no approved disease-modifying treatments. These findings, which will be presented today at the 2026 American Academy of Neurology (AAN) annual meeting, build on previously reported positive topline data and provide a more comprehensive view of treatment effect across multiple clinically meaningful domains.

The study met its primary endpoint in individuals ≥5 years of age, with zilganersen 50 mg demonstrating statistically significant and clinically meaningful stabilization of gait speed as assessed by the 10-Meter Walk Test (10MWT), compared to control at Week 61. The 10MWT is a commonly used measure of gross motor function in neurologic disease. New data from the Gross Motor Function Measure-88 (GMFM-88), a well-established motor endpoint, supports the primary outcome of the study by demonstrating that treatment with zilganersen may improve gross motor function in younger children (2-4 years of age), compared to control. Key secondary endpoint results from patient/caregiver- and clinician-reported outcome assessments consistently favored zilganersen. Zilganersen demonstrated favorable safety and tolerability.