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FDA approves first Alexander disease treatment, Ionis's Zanvastro

FDA approves first Alexander disease treatment, Ionis's Zanvastro

New Capabilities

Approval is Ionis's first independent neurology launch, validating its rare disease pipeline

September 7th, 2026: Fierce Biotech publishes feature

Overview

Updated Sep 13

Jenny Pearson's daughter Elise had her first seizure at 16 months. A scan a year later showed white splotches on her frontal lobe, and a genetic test confirmed Alexander disease, a rare progressive neurological disorder that had no treatment.

On September 3, the FDA approved Zanvastro (zilganersen), made by Ionis Pharmaceuticals, for children and adults with Alexander disease. The drug cuts production of the abnormal protein that drives the disease; in a 54-patient trial, walking speed held nearly steady over 61 weeks while untreated patients declined 35.4%. It costs $285,000 per dose, about $1.14 million a year.

Why it matters

For the roughly 1 in a million people with Alexander disease, there is now a treatment that slows the disease's progression.

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Key Indicators

$285,000
Price per dose
Zanvastro is priced at $285,000 per intrathecal injection, about $1.14 million per year at four doses.
33.3%
Gait speed difference vs control
In the pivotal trial, walking speed held nearly steady on Zanvastro (down 2.1%) while untreated patients declined 35.4% at 61 weeks; between-group difference 33.3% (p=0.041).
54
Participants in pivotal study
The global Phase 1-3 study enrolled 54 patients aged 1.5 to 53 years across 13 sites in eight countries.
2
Independent launches in 2026
Ionis expanded Tryngolza's approval in June and launched Zanvastro in September, its first two products commercialized without a partner.
33.6%
GFAP biomarker shift vs control
Plasma GFAP, the protein that builds up in Alexander disease, changed 33.6% more in treated patients than controls at week 61 (p=0.003).
22.9%
Motor function gain in ages 2-4
Children aged 2 to 4 scored 22.9% better than controls on the Gross Motor Function Measure-88 at week 61 (p=0.034).

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People Involved

Brett P. Monia
Brett P. Monia
Chief executive officer, Ionis Pharmaceuticals
Leading Ionis's independent commercialization push
 Jenny Pearson
Jenny Pearson
Mother of Elise, a patient with Alexander disease
Daughter Elise diagnosed with Alexander disease

Organizations Involved

Ionis Pharmaceuticals
Ionis Pharmaceuticals
Biotechnology company
Developer of Zanvastro, now launching independently

RNA-targeted drug developer based in Carlsbad, California.
U.S. Food and Drug Administration
U.S. Food and Drug Administration
Federal Regulatory Agency
Approved Zanvastro

The U.S. agency that approves drugs and medical devices.
Recordati
Recordati
Pharmaceutical company
Holds ex-US rights to zilganersen

Italian pharmaceutical company focused on specialty and rare diseases.

Timeline

1949 September 2026

7 events Latest: September 7th, 2026 · 2 months ago
Tap a bar to jump to that date

  1. Fierce Biotech publishes feature

    Latest Media

    Feature on the approval opens with the story of patient Elise Pearson.

  2. FDA approves Zanvastro

    Regulatory

    First approved treatment for Alexander disease, for pediatric and adult patients.

  3. Tryngolza label expanded to severe hypertriglyceridemia

    Regulatory

    FDA cleared Tryngolza (olezarsen) for severe hypertriglyceridemia, Ionis's first independent launch. The drug was first approved in 2024 for familial chylomicronemia syndrome.

  4. Recordati license agreement

    Business

    Recordati obtains ex-US rights to zilganersen, plans Europe and Japan submissions in 2027.

  5. Pivotal study begins

    Clinical trial

    Phase 1-3 study (NCT04849741) begins enrolling patients with Alexander disease.

  6. GFAP gene identified as cause

    Medical discovery

    Mutations in the GFAP gene identified as the cause of Alexander disease.

  7. Alexander disease first described

    Medical discovery

    W. Stewart Alexander first described the disease that would bear his name.

Scenarios

1

Zanvastro sales ramp as Alexander disease community gains access

Possible Resolves by End of 2027

Discussed by: William Blair analysts, BioSpace

Ionis's independent commercialization infrastructure faces its first neurology test. The ultra-rare disease means a small patient population, but the $285,000 per dose price, about $1.14 million per year, could generate meaningful revenue. Ionis expects US availability within weeks.

2

Europe and Japan approve zilganersen, expanding the market

Likely Resolves by End of 2028

Discussed by: Ionis, Recordati

Recordati holds ex-US rights and plans regulatory submissions in Europe and Japan in 2027. Approvals would expand the addressable patient population and validate the partnership model.

3

Angelman syndrome drug succeeds, validating Ionis neurology pipeline

Uncertain Resolves by Q2 2028

Discussed by: BioSpace, Ionis

The Zanvastro approval gives Ionis a footprint in neurology. The next test is obudanersen, an RNA-based therapy for Angelman syndrome, in the Phase 3 REVEAL study. Success would confirm the platform's broader potential.

4

Payer requirements slow patient access to Zanvastro

Possible Resolves by Q3 2027

Discussed by: Medical Daily, PharmaDeviceNews

The $285,000-per-dose price and intrathecal delivery create access hurdles. Medical Daily expects prior authorization, genetic confirmation of a GFAP variant, and possible site-of-care restrictions. Ionis says it will help with insurance approval and affordability programs.

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

December 2016

Spinraza for spinal muscular atrophy (2016)

Ionis developed nusinersen, an antisense oligonucleotide delivered intrathecally, for spinal muscular atrophy. It was the first treatment for SMA and became a blockbuster, with Biogen commercializing it.

Then

Approved by FDA in December 2016, became standard of care for SMA.

Now

Proved antisense oligonucleotides could treat neurological diseases, generating billions in revenue.

Why this matters now

Same company, same modality, same delivery route. Zanvastro is the second intrathecal antisense drug from Ionis to reach approval.

September 2016

Exondys 51 for Duchenne muscular dystrophy (2016)

Sarepta Therapeutics won FDA approval for eteplirsen, an antisense oligonucleotide for Duchenne muscular dystrophy, despite a tiny trial and a surrogate endpoint. The approval was controversial.

Then

Approved via accelerated pathway, became a commercial success.

Now

Showed FDA willingness to approve ultra-rare disease drugs with limited data.

Why this matters now

Demonstrates the regulatory path for ultra-rare disease drugs with small trials, similar to Zanvastro's 54-patient study.

1998-2026

Antisense oligonucleotides come of age (1998-2026)

The first antisense drug, fomivirsen, was approved in 1998 but failed commercially. The field struggled for two decades before a wave of approvals for rare diseases, including Spinraza, Tryngolza, and now Zanvastro.

Then

Early antisense drugs failed commercially, nearly killing the field.

Now

The platform now underpins multiple approved drugs for rare diseases.

Why this matters now

Zanvastro is the latest validation of a platform Ionis has spent three decades developing.

Sources

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+5
U.S. Food and Drug Administration STAT News BioSpace U.S. Securities and Exchange Commission Fierce Biotech Rallies PharmExec StockTitan Healio Medical Daily PharmaDeviceNews