Ionis wins first-ever FDA approval for Alexander disease therapy

The FDA approved Ionis Pharmaceuticals’ zilganersen, marketed as Zanvastro, on Sept. 3, 2026 as the first treatment for Alexander disease, an ultra-rare, progressive genetic neurological disorder affecting fewer than 1,000 people in the U.S.

The antisense/RNA-targeted therapy lowers production of GFAP, a protein that builds up abnormally in the brain and contributes to disease progression. It is approved for both pediatric and adult patients.

Approval was supported by a pivotal study in which the 50-mg dose produced statistically significant stabilization of gait speed at 61 weeks versus control; reported data showed a 33.3% mean difference on the 10-meter walk test.

Zanvastro had received Breakthrough Therapy, Orphan Drug and Rare Pediatric Disease designations. FDA approval arrived ahead of its previously scheduled Sept. 22 action date.

For Ionis, this is its first independent launch from its neurology portfolio and a commercial proof point for its RNA-targeted platform in rare neurodegenerative disease. The company views it as infrastructure and validation for subsequent rare pediatric neurology programs, including work in Angelman syndrome.

Ionis retains U.S. commercialization rights. In June, it licensed rights outside the U.S. to Recordati, while continuing to lead global development.