Ultragenyx Stock Jumps on Landmark FDA Approval -- Barrons.com

By Mariapaula Gonzalez

Shares of Ultragenyx jumped Thursday after the Food and Drug Administration approved a first-of-its-kind treatment for pediatric patients with a rare neurodevelopmental disease.

Ultragenyx stock closed up 13% to $14.50 on Thursday.

The FDA said in a press release that it approved Ultragenyx's Fayuvi for treatment of pediatric patients with mucopolysaccharidosis type IIIA-also known as Sanfilippo syndrome Type A-a rare inherited disease that progressively damages the brain and nervous system, resulting in the gradual loss of developmental abilities in children.

The gene therapy, which is manufactured at two specialized facilities in Massachusetts and Ohio, is administered once through a standard infusion that delivers it straight into the bloodstream. To get the treatment inside the brain, scientists use AAV9, a harmless, modified virus that crosses from the blood into the brain and central nervous system.

The FDA granted approval based on up to eight years of clinical trial data. In Ultragenyx's studies, children who received the therapy scored 23.5 points higher on cognitive tests than untreated patients did. Because the disease causes toxic waste-called heparan sulfate-to accumulate in brain fluid and damage cells, scientists tracked these waste levels directly, finding that the therapy continuously cleared out the buildup over time.

Fayuvi will be available exclusively at Qualified Treatment Centers, specialized hospitals that are trained to administer gene therapies. Within the next few days, Ultragenyx will launch a website listing the authorized locations, and it expects to ship the therapy to them within 30 to 60 days.

The company said there are roughly 3,000 to 5,000 children living with Sanfilippo syndrome Type A in areas where the drug will be accessible. The average life expectancy for untreated patients is around 15 years.

Fayuvi marks Ultragenyx's second gene therapy approval and sixth FDA approval.

Before Thursday, there was no FDA-approved therapy designed to stop or change the root of the disease, and doctors could manage only individual symptoms,.

Write to Mariapaula Gonzalez at mariapaula.gonzalez@barrons.com

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September 17, 2026 17:13 ET (21:13 GMT)