A first treatment for Alexander disease, using a gene-silencing medicine
What happened
On 3 September 2026, the United States Food and Drug Administration approved the first medicine to treat Alexander disease. The medicine is called Zanvastro. Its ingredient name is zilganersen, and it is made by Ionis Pharmaceuticals. Alexander disease is very rare. It affects fewer than one in a million people. It is caused by a fault in a gene that makes a protein called GFAP. Because of the fault, an abnormal version of the protein builds up in certain brain cells and damages the nervous system. The effects are severe. They can include seizures, delays in development, difficulty walking, muscle weakness and raised pressure inside the brain. Until now there was no treatment that tackled the cause. Care was about managing symptoms. Zanvastro works differently. It is what is called an antisense oligonucleotide. Think of it as a small piece of genetic material designed to switch down the instructions for making the faulty protein, so less of it is produced in the first place. It is given as an injection into the fluid around the spine, once every three months.
Why this matters
This is a US approval, so it does not change what is available on the NHS today. A separate decision by the UK's MHRA would be needed before it could be prescribed here, and then NICE would look at whether the NHS should fund it. So why write about it at all? Because of what the technology represents. Antisense medicines are a family of treatments that target the genetic instructions behind a disease, rather than its symptoms. The same approach has already produced treatments for other rare neurological conditions. Each approval makes the next one a little more likely, because regulators, researchers and manufacturers learn how to design the trials and measure the results. For families living with an ultra-rare condition, that matters enormously. Rare diseases have historically been left behind, because so few patients means so little commercial interest. Approvals like this one show the route is now real. It also matters for how we think about rare disease trials in general. Recruiting 53 patients worldwide for one condition is genuinely difficult, and doing it properly deserves recognition.
What the evidence actually says
The approval was based on a randomised controlled trial of 49 children and adults aged two and over, plus an open-label sub-study of four additional patients under the age of two. That is 53 people in total. In patients aged five and over, those on the medicine had significantly better walking speed at 61 weeks than those who were not treated. In the younger children aged two to four, the treated group showed improvements in motor skills while the untreated comparison group declined. Common side effects reported were vomiting, back pain, cough and headache. There were also cases of post-lumbar puncture syndrome, which is a headache that can follow a spinal injection, and aseptic meningitis, which is inflammation of the lining of the brain and spinal cord not caused by bacteria. In the FDA's announcement, Dr Emily Freilich described the approval as 'a landmark moment for this community, offering the first therapy that addresses the underlying cause'. A few things to hold in mind. A trial of 53 people is small in absolute terms, though very large for a condition this rare. Better walking speed over 61 weeks is a meaningful result, but it is not the same as showing the disease has been stopped. Longer follow-up will be needed to see how much difference it makes over years rather than months. The medicine received orphan drug, fast track, breakthrough therapy and rare paediatric disease designations. These speed up review; they do not lower the bar for showing a benefit.
Practical advice
If this condition affects your family, the useful next steps are these. Speak to your specialist team rather than acting on news reports. They will know whether a UK licence application is expected, and whether any UK trial or early access route exists. Ask about patient registries. For rare conditions, registries are often how families hear first about new trials. UK charities that support families with rare neurological conditions can help you find others in the same position, and they usually track approvals across different countries. For everyone else, the sensible takeaway is simpler. When you read that a drug has been 'approved', always check where. A US approval is not a UK approval, and neither automatically means the NHS will fund it. And be wary of anyone offering to sell you an unlicensed medicine from overseas. Medicines given by spinal injection every three months are hospital treatments, not something to arrange privately online.
What to know
On 3 September 2026 the US FDA approved Zanvastro (zilganersen) as the first treatment for Alexander disease, a very rare inherited condition affecting the brain and nervous system. It is a gene-silencing medicine that reduces production of the faulty protein causing the damage. It is given by spinal injection every three months. Approval was based on a trial of 49 patients aged two and over, plus four younger children. Patients aged five and over walked faster at 61 weeks than untreated comparisons. Side effects included vomiting, back pain, cough, headache, post-lumbar puncture headache and aseptic meningitis. This is a United States approval. It does not mean the medicine is available in the UK. That would need MHRA authorisation and, for NHS funding, a NICE decision. Sources: US Food and Drug Administration, 'FDA Approves First Drug to Treat Alexander Disease', 3 September 2026, https://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-treat-alexander-disease ; US Food and Drug Administration press announcements, accessed 7 September 2026, https://www.fda.gov/news-events/fda-newsroom/press-announcements ; MHRA, 'Medicines and Healthcare products Regulatory Agency', accessed 7 September 2026, https://www.gov.uk/government/organisations/medicines-and-healthcare-products-regulatory-agency This article is for general information and does not replace advice from a doctor, pharmacist or other qualified healthcare professional. Treatment decisions for rare conditions should always be made with a specialist team.
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