Ionis Pharmaceuticals' Zilganersen Shows Positive Results in Alexander Disease Study

By Chris Stiles • Tuesday, April 21 14:14 • Permanent Link

Ionis Pharmaceuticals said its investigational drug zilganersen produced additional positive results in a pivotal study in Alexander disease, showing gains across gait, gross motor function and multiple patient* and clinician-reported measures ahead of an FDA decision due Sept. 22, 2026.

In the 60-week double-blind portion of the phase 1-3 study, zilganersen met its main endpoint in patients age 5 and older, with a 33.3% least-square mean difference in gait speed on the 10-meter walk test versus control at week 61. In children ages 2 to 4, the Gross Motor Function Measure-88 showed a 22.9-point least-square mean difference versus control.

On symptom measures, 32% of patients on zilganersen said their most bothersome symptom was “much better,” versus 0% on control. Only 5% on zilganersen said it was “much worse,” compared with 31% on control.

For overall disease severity, 83% of patients on zilganersen reported improvement or no change, versus 76% on control. Worsening was reported by 17% on zilganersen and 24% on control.

On overall change, 21% of patients on zilganersen said they felt “much better,” compared with 0% on control. Just 4% said they felt “much worse,” versus 18% on control.

Clinicians rated 75% of zilganersen-treated patients as improved or unchanged, compared with 47% on control. They rated 25% of zilganersen patients as “a little worse” and 0% as “much worse,” versus 41% and 12% on control, respectively.

Ionis said exploratory testing showed plasma GFAP levels fell 33.6% at week 61 versus control.

The study enrolled 53 people with Alexander disease ages 2 to 53 years in the pivotal analysis, with 54 participants enrolled overall across 13 sites in eight countries. Ionis said serious treatment-emergent adverse events occurred in 37.5% of patients receiving zilganersen 25 mg or 50 mg, compared with 47.1% in pooled control. As a result of these announcements, the company's shares have moved 2.12% on the market, and are now trading at a price of $74.24. For more information, read the company's full 8-K submission here.

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