IONS Edges Up After-Hours On FDA’s Green Light For Neurology Drug After Being Dragged Down By Ultragenyx’s Failed Trial

Zanvastro is now approved for children and adults with Alexander disease, a rare and often fatal brain condition that affects fewer than one in a million people.

• IONS stock fell during regular trading after Ultragenyx reported on Wednesday that its experimental Angelman syndrome drug failed in a late-stage study. 
• Zanvastro is Ionis’s first independent neurology launch, after Tryngolza for high triglycerides and Dawnzera for hereditary angioedema.
• GSK’s bepirovirsen, a hepatitis B drug discovered by Ionis, has an FDA decision due on Oct. 26.

Ionis Pharmaceuticals (IONS) shares edged up 1% after-hours on Thursday after the U.S. Food and Drug Administration (FDA) approved its drug Zanvastro as the first treatment for Alexander disease ahead of its own deadline.

The stock had fallen about 6% in regular trading after Ultragenyx reported on Wednesday that its experimental Angelman syndrome drug failed in a late-stage study, dragging down Ionis, which is also developing a drug for the rare genetic brain disorder.

What The FDA Cleared

Zanvastro is approved for children and adults with Alexander disease, a rare and often fatal brain condition that affects fewer than one in a million people. Until now, families had only supportive care. The drug will be given as a spinal injection every three months and works by lowering a harmful protein that builds up in the brain.

In a study of 49 patients aged 2 and older, people treated with Zanvastro walked better at about 14 months than those who were not treated. Younger children also maintained or gained motor skills, whereas untreated children declined. The most common side effects were vomiting, back pain, cough, headache, and after-effects from the spinal tap.

The FDA approval came nearly three weeks ahead of the September 22 review deadline.

What This Means For Ionis’s Pipeline

Zanvastro is Ionis’s first independent neurology launch, after Tryngolza for high triglycerides and Dawnzera for hereditary angioedema. It is a template for other wholly owned brain drugs, starting with obudanersen for Angelman syndrome, which has finished pivotal trial enrollment, with results expected in the second half of 2027.

Ionis’s other five approved drugs are sold mainly with partners: Spinraza and Qalsody with Biogen, Wainua with AstraZeneca, plus Tegsedi and Waylivra.

Other Near-Term Catalysts

The company’s next near-term tests are larger. GSK’s bepirovirsen, a hepatitis B drug discovered by Ionis, has an FDA decision due October 26. Novartis is expected to report results from the pelacarsen heart-disease study later this year, a potential royalty stream if the data are strong.

Ionis also has a late-2026 readout of ulefnersen in a rare form of amyotrophic lateral sclerosis.

How Did IONS Retail Traders React?

On Stocktwits, retail sentiment around IONS stock improved from ‘bearish’ to ‘neutral’ over the past 24 hours, while message volume stayed at ‘low’ levels.

IONS stock has fallen 27% year-to-date. 

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