Zilganersen FDA Decision Date: 2026-09-22

September 22, 2026

FDA decision expected

FDA assigned a September 22, 2026 PDUFA target action date to the zilganersen NDA.

April 21, 2026

Additional pivotal-study results were presented

At the AAN annual meeting, Ionis reported additional treatment effects across clinically meaningful symptom domains and biomarker analyses.

Ionis — Zilganersen data at AAN 2026↗

March 23, 2026

FDA accepted the NDA with Priority Review

FDA accepted the application based on the pivotal Phase 1-3 study and granted Priority Review.

Ionis — NDA acceptance and Priority Review↗

January 2026

Ionis submitted the NDA

Ionis submitted the zilganersen NDA after the pivotal study demonstrated a clinically meaningful effect in children and adults with Alexander disease.

Ionis — 2025 annual report and NDA submission↗

December 2, 2025

FDA granted Breakthrough Therapy designation

FDA granted Breakthrough Therapy designation based on the pivotal-study results.

Ionis — Breakthrough Therapy designation↗

September 22, 2025

The pivotal study reported positive topline results

Zilganersen demonstrated statistically significant and clinically meaningful stabilization on the primary gait-speed endpoint, with key secondary endpoints favoring treatment.

Ionis — Positive pivotal-study topline results↗

Zilganersen

Alexander disease · Children and adults with Alexander disease

IONS · Ionis Pharmaceuticals, Inc.

Regulatory designations

Priority Review FDA

Breakthrough Therapy FDA

Orphan Drug FDA

Rare Pediatric Disease FDA

Orphan Drug EMA

Full timeline