Zanvastro (zilganersen)
An approved treatment for Alexander Disease.
The same compound appears under different names depending on the context. Here is how to identify Zilganersen wherever you encounter it, plus the key facts at a glance.
- Generic name
- Zilganersen
- Brand name
- Zanvastro
- Development code
- ION373
- Drug class
- Antisense oligonucleotide
- Manufacturer
- Ionis Pharmaceuticals
- How it's taken
- Zanvastro 50 mg is given as an injection into the spinal fluid (called an intrathecal injection) once every 3 months.
The first and only approved treatment for Alexander disease. It lowers levels of glial fibrillary acidic protein (GFAP), the protein that builds up abnormally in Alexander disease and damages brain cells.
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Where Zilganersen fits
The first and only disease-modifying treatment for Alexander disease. Until its approval, care was limited to managing individual symptoms such as seizures, feeding difficulty, and mobility loss.
How Zilganersen works
Zanvastro stops your body from making too much of a protein called GFAP. In Alexander disease, a gene change causes overproduction of this protein, which damages the brain cells called astrocytes that support nerve cells. This medicine targets the instructions for making GFAP and turns them down, kind of like turning down the volume on a speaker that's too loud. It is the first treatment that works on the cause of the disease rather than only the symptoms.
Mechanism: Antisense oligonucleotide that reduces GFAP protein production
Side effects and safety
The most common side effects (in more than 25% of patients) were vomiting, back pain, cough, headache, and headache after the spinal injection. Some patients developed aseptic meningitis, which is irritation of the lining around the brain and spinal cord. Call your doctor right away if you have a severe headache, a stiff neck, or a fever. Most side effects were mild or moderate, and serious side effects happened less often in patients on Zanvastro than in the control group.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Zilganersen
Zanvastro 50 mg is given as an injection into the spinal fluid (called an intrathecal injection) once every 3 months. It's given through a lumbar puncture (a needle placed in the lower back) by healthcare professionals experienced in doing lumbar punctures.
Availability and cost
Only available as the brand-name product.
Help paying for Zanvastro
Pick your insurance to see which help fits. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE; charity funds are the usual route there.
- Copay help
Ionis Every Step Copay Program: commercially insured patients may pay as little as $0 out of pocket for each ZANVASTRO dose. Not available to anyone using Medicare, Medicaid, TRICARE, Department of Defense, VA or any other state or federal government-funded plan.
For: private insurance · source - Infusion cost help
The Copay Program also covers administration costs, so eligible commercially insured patients may pay as little as $0 for each dose and its administration. Terms, conditions and limits apply, and the program may change or end, including in specific states.
For: private insurance · source - Insurance and case manager help
Helps people with Alexander disease get started on ZANVASTRO, gives ongoing support from a dedicated Patient Education Manager, helps with insurance approval, and helps navigate financial assistance options.
The official page does not say who qualifies. Ask the program. · source
Good to know: Enrollment in Ionis Every Step (consent form online, enrollment form at the doctor's office, or by phone) is required for all affordability programs. No free-drug or bridge program is published yet. Phone line Mon-Fri 9 AM-6 PM ET.
- From a charity · United Leukodystrophy FoundationHultman Memorial Fund fundOpen
Pays for: Expenses directly related to the affected family member, based on demonstrated hardship (per 12 months), up to $500 per year.
The foundation says: “Applications are reviewed on a rolling basis as funding is available.”
Clinical trial results
The FDA approved Zanvastro on September 3, 2026. The pivotal study (NCT04849741) ran at 13 sites in 8 countries. Its main, controlled part enrolled 49 people with Alexander disease ages 2 and older, and a separate open-label part enrolled 4 children under age 2. Patients 5 and older taking the 50 mg dose held their walking speed steady on the 10-Meter Walk Test compared with the control group at week 61 (a 33.3% difference, p=0.041). Children ages 2 to 4 showed improvement in gross motor function on the GMFM-88 scale. Patient, caregiver, and clinician ratings all favored Zanvastro.
Development history
Developed by Ionis Pharmaceuticals, zilganersen entered its pivotal clinical trial for Alexander disease in 2021. The FDA approved it as Zanvastro on September 3, 2026, making it the first treatment ever approved for the condition, and granted Ionis a Rare Pediatric Disease Priority Review Voucher alongside the approval. In June 2026, Ionis licensed rights outside the U.S. to Recordati, which plans regulatory submissions in Europe and Japan in 2027.
Explore Alexander Disease trials
Common questions about Zilganersen
▸What is Zilganersen (Zanvastro)?
The first and only approved treatment for Alexander disease. It lowers levels of glial fibrillary acidic protein (GFAP), the protein that builds up abnormally in Alexander disease and damages brain cells.
▸How does Zilganersen work?
Zanvastro stops your body from making too much of a protein called GFAP. In Alexander disease, a gene change causes overproduction of this protein, which damages the brain cells called astrocytes that support nerve cells. This medicine targets the instructions for making GFAP and turns them down, kind of like turning down the volume on a speaker that's too loud. It is the first treatment that works on the cause of the disease rather than only the symptoms.
▸What are the side effects of Zilganersen?
The most common side effects (in more than 25% of patients) were vomiting, back pain, cough, headache, and headache after the spinal injection. Some patients developed aseptic meningitis, which is irritation of the lining around the brain and spinal cord. Call your doctor right away if you have a severe headache, a stiff neck, or a fever. Most side effects were mild or moderate, and serious side effects happened less often in patients on Zanvastro than in the control group.
▸How is Zilganersen taken?
Zanvastro 50 mg is given as an injection into the spinal fluid (called an intrathecal injection) once every 3 months. It's given through a lumbar puncture (a needle placed in the lower back) by healthcare professionals experienced in doing lumbar punctures.
▸Is Zilganersen FDA approved?
Yes, Zilganersen (Zanvastro) is FDA approved (2026) for the treatment of Alexander Disease.
▸What is Alexander disease?
Alexander disease is an extremely rare and often fatal neurodegenerative disorder caused by changes in the GFAP gene, which lead to toxic buildup of GFAP protein in brain cells called astrocytes. It affects about 1 in 1 to 3 million people worldwide. Zanvastro (zilganersen), approved in September 2026, is the first treatment for it.
▸How does zilganersen work?
Zilganersen is an antisense oligonucleotide that reduces production of GFAP protein by targeting the GFAP gene's instructions. By reducing the toxic protein buildup that damages the brain, it addresses the underlying cause of the disease rather than only its symptoms.
▸What is the current development status?
The FDA approved zilganersen as Zanvastro on September 3, 2026 for adults and children with Alexander disease. Ionis said it would be available in the U.S. within a few weeks of approval. Submissions in Europe and Japan are expected in 2027 through Ionis' partner Recordati.
▸How is zilganersen administered?
Zanvastro is given by intrathecal injection (into the spinal fluid) once every 3 months at a dose of 50 mg. This delivers the medicine directly to the central nervous system, where the GFAP buildup causes damage.
▸What unmet need does zilganersen address?
Before Zanvastro, there was no treatment for Alexander disease and care focused only on managing symptoms. Zanvastro is the first medicine that addresses the root cause of the disease by reducing the toxic GFAP protein, and in its pivotal study it kept patients' walking speed from declining.