Ultragenyx rises as gene therapy shows long‑term benefit in rare childhood brain disorder

Shares of drugmaker Ultragenyx RARE.O rise 4% to $25.75 in premarket trading

Co says its experimental gene therapy helps children with Sanfilippo syndrome Type A - a rare disorder that rapidly damages the brain - retain key abilities for more than eight years

Sanfilippo Type A happens when the body cannot break down certain substances, leading to severe brain decline; most children die in their teens, according to co

Co says treated children kept skills like walking, communicating and eating independently, while most untreated kids lose these abilities early

Co's therapy, UX111, given as one-time infusion; most common side effect was temporary liver enzyme increase

RARE resubmits FDA application for accelerated approval; expects decision in Q3 2026, co says

Shares down ~45% in 2025