FDA approved Ionis ZANVASTRO (zilganersen) for Alexander disease in pediatric and adult patients.

The U.S. Food and Drug Administration approved ZANVASTRO (zilganersen) for Alexander disease in pediatric and adult patients, Ionis Pharmaceuticals said in a September 3, 2026 press release furnished with Form 8-K AccNo 0001140361-26-035657. The company filing describes ZANVASTRO as the first and only disease-modifying treatment for AxD.

Ionis Pharmaceuticals, Inc. (Nasdaq: IONS) disclosed the decision in Form 8-K AccNo 0001140361-26-035657 (Date of earliest event September 3, 2026; Items 7.01, 8.01, and 9.01). The SEC index shows Filing Date 2026-09-04 and Accepted 2026-09-04 at 06:01:59 ET. Item 7.01 furnishes Exhibit 99.1; Item 8.01 restates the approval as an Other Event. The exhibit is Carlsbad-dated September 3, 2026.

What the decision covers

The filing states the FDA approved ZANVASTRO (zilganersen) for the treatment of Alexander disease (AxD) in pediatric and adult patients. Ionis’s 8-K and Exhibit 99.1 characterize ZANVASTRO as the first and only disease-modifying treatment for AxD — company language in the furnished release and Item 8.01, not a separate FDA “first” finding printed as a label quote here. Until now, the company says, treatment of AxD has primarily been limited to managing symptoms.

AxD is described as an ultra-rare, progressive, and often fatal neurological disorder that can affect motor, cognitive, autonomic, and gastrointestinal function. The exhibit estimates AxD affects approximately 1 in 1 to 3 million people worldwide. Those prevalence figures are company statements in the note. The “About Alexander Disease” section of Exhibit 99.1 also states AxD usually leads to death within 14 to 25 years after symptom onset.

How the medicine is described

ZANVASTRO is an RNA-targeted medicine designed to reduce production of glial fibrillary acidic protein (GFAP). AxD is caused by changes in the GFAP gene that lead to overproduction and toxic accumulation of GFAP in astrocytes. ZANVASTRO 50 mg is administered quarterly as an intrathecal injection.

The pivotal numbers as printed

FDA approval, as printed in Item 8.01 and Exhibit 99.1, rested on positive results from the pivotal study of ZANVASTRO in people living with AxD. In individuals 5 years of age and older, the study met its primary endpoint: ZANVASTRO 50 mg demonstrated statistically significant and clinically meaningful stabilization of gait speed on the 10-Meter Walk Test compared with control at Week 61, with a least square mean difference of 33.3% (p=0.041).

In patients 2 to 4 years of age, ZANVASTRO demonstrated improvement in gross motor function versus control at Week 61 on the Gross Motor Function Measure-88 (GMFM-88). Secondary and exploratory endpoint results from patient/caregiver- and clinician-reported outcome assessments, the company says, consistently favored ZANVASTRO.

Exhibit 99.1’s study synopsis identifies the program as a global, multicenter, randomized, double-blind, controlled, multiple-ascending-dose Phase 1-3 study (NCT04849741). It enrolled 54 participants with AxD between ages 1.5 and 53 years across 13 sites in eight countries, randomized 2:1 to ZANVASTRO or control for a 60-week double-blind period. Dose cohorts were 25 mg and 50 mg, with the 50 mg cohort analyzed as the pivotal dose cohort and dosing every 12 weeks.

Safety as printed

The company states ZANVASTRO demonstrated a favorable safety and tolerability profile, with most adverse events mild or moderate in severity, and serious treatment-emergent adverse events occurring less frequently in the ZANVASTRO group than in control.

Exhibit 99.1’s Important Safety Information warns of aseptic meningitis: if symptoms consistent with aseptic meningitis develop, diagnostic workup and treatment should be initiated according to the standard of care. The exhibit reports adverse reactions of aseptic meningitis in patients treated with ZANVASTRO during Study 1, including one patient with a serious aseptic meningitis reaction in the double-blind period that reoccurred in the open-label extension and required dose interruption and pretreatment with intravenous dexamethasone before subsequent doses.

Most common adverse reactions (incidence ≥25% in patients treated with ZANVASTRO and greater than control) were vomiting, back pain, cough, headache, and post-lumbar puncture syndrome. The exhibit says adverse reactions in patients younger than 2 years of age are expected to be similar to those in pediatric patients 2 years and older, and points readers to the full Prescribing Information.

Commercial next steps in the note

Ionis says ZANVASTRO will be available in the United States in the coming weeks. With the approval, the FDA granted Ionis a Rare Pediatric Disease Priority Review Voucher. Exhibit 99.1 frames the product as Ionis’s first independent launch from its neurology pipeline and its second independent launch this year.

In June 2026, Ionis entered a license agreement with Recordati under which Recordati obtained exclusive rights to develop and commercialize zilganersen in all countries outside the United States. Ionis says it is working with Recordati on regulatory submissions in Europe and Japan, expected in 2027. The company also describes Ionis Every Step patient-support services for people prescribed ZANVASTRO. A company webcast is scheduled for Friday, September 4, 2026, at 10:00 a.m. ET.

No list price, wholesale acquisition cost, peak-sales figure, or market reaction appears in AccNo 0001140361-26-035657. This package does not cover Liquidia’s YUTREPIA Fast Track designation — a separate designation story, not this FDA approval.

Still open after this filing

Full Prescribing Information text beyond the Important Safety Information excerpted in Exhibit 99.1. U.S. list price and payer coverage terms. Exact U.S. commercial availability date within “the coming weeks.” Whether and when the Rare Pediatric Disease Priority Review Voucher is used or transferred. Timing and outcome of Recordati’s Europe and Japan submissions expected in 2027. Companies/IONS on tickergrove.com may soft-404 and is not required for this filing story.