Ionis reports positive zilganersen data for Alexander disease

Ionis Pharmaceuticals Inc. (NASDAQ: IONS) presented additional data from its pivotal study of zilganersen for Alexander disease at the 2026 American Academy of Neurology annual meeting. The study met its primary endpoint in individuals aged 5 years and older, with zilganersen 50 mg demonstrating statistically significant stabilization of gait speed compared to control at week 61.

The Phase 1-3 study included 53 people with Alexander disease aged 2 to 53 years. Zilganersen resulted in a 33.3% improvement in gait speed on the 10-Meter Walk Test compared to control. In children aged 2-4 years, the Gross Motor Function Measure-88 showed a 22.9-point improvement compared to control.

Secondary endpoints favored zilganersen across multiple measures. In the zilganersen group, 32% of patients rated their most bothersome symptom as "much better" compared to 0% on control. For overall disease severity, 83% of patients receiving zilganersen reported improvement or no change compared to 76% on control.

Alexander disease is a rare, progressive neurological condition affecting approximately 1 per 1 to 3 million people worldwide. The disease is caused by overproduction of glial fibrillary acidic protein and currently has no approved disease-modifying treatments. Zilganersen is designed to reduce this protein overproduction.

The drug demonstrated favorable safety and tolerability, with serious treatment-emergent adverse events occurring less frequently in the zilganersen group compared to control (37.5% versus 47.1%). Zilganersen is under Priority Review by the FDA with a PDUFA action date of September 22, 2026.

The information is based on a company press release.

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