Ultragenyx gets FDA approval for glycogen storage disease gene therapy

The U.S. FDA has granted accelerated approval to Ultragenyx Pharmaceutical’s gene therapy, Genglycos (pariglasgene brecaparvovec-opnr), in adult and pediatric patients eight years and older with glycogen storage disease type Ia (GSDIa).

GSDIa is an ultra-rare genetic metabolic disorder caused by a deficiency of the enzyme needed to release glucose from the liver to the bloodstream. The deficiency reduces the liver’s ability to control glucose levels and is associated with potentially life-threatening hypoglycemia episodes and other serious complications, requiring rigorous nutritional management that involves a burdensome, around-the-clock regimen of raw cornstarch intake.

Genglycos, Ultragenyx’s first gene therapy approval, is a one-time AAV8 based gene therapy designed to deliver a functional G6PC gene to the liver, aiming to restore the deficient enzyme required to release stored glucose and ensure stable blood sugar levels when a person is fasting.

As part of the accelerated approval, Ultragenyx will provide two years of safety and efficacy data from 50 commercially treated patients and 20 control patients through an expanded disease monitoring program. The control group will include patients who sought treatment but were ineligible for Genglycos due to anti-AAV8 antibodies. The program will assess cornstarch requirements, fasting tolerance and other measures, while continuing to monitor previously treated trial participants and new commercial patients for up to 10 years.

The approval is good news for Ultragenyx after some rough goings. After getting hit with a CRL for its AAV9 gene therapy, UX111, as a treatment for patients with Sanfilippo syndrome type in July 2025, Ultragenyx resubmitted its BLA, only to receive an incomplete response letter in February 2026. At the same time, the company unveiled restructuring plan, laying off 10% of workforce.