FDA Approves Gene Therapy for Glycogen Storage Disease

The Food and Drug Administration has granted accelerated approval to pariglasgene brecaparvovec-opnr (Genglycos, Ultragenyx) as the first treatment for adults and pediatric patients aged 8 years and older with glycogen storage disease type Ia (GSDIa).

GSDIa is a rare, inherited disorder caused by a deficiency of glucose-6-phosphatase (G6PC), an enzyme that releases free glucose from the liver and kidneys into the bloodstream. Without it, blood sugar drops dangerously low during fasting. The condition is managed through frequent meals and around-the-clock supplementation with uncooked cornstarch.

Pariglasgene brecaparvovec-opnr is a one-time adeno-associated virus serotype 8 (AAV8)-based gene therapy that delivers a functional G6PC gene to hepatocytes resulting in production of normally functioning glucose-6-phosphatase. It is indicated as an adjunct to nutritional management to reduce daily cornstarch intake.

FDA based its approval on a randomized, double-blind, placebo-controlled study in which patients followed for 48 weeks showed a statistically significant 31% mean reduction in daily cornstarch intake compared with placebo. The reduction in cornstarch intake served as the surrogate endpoint for the accelerated approval.

The application received a Rare Pediatric Disease Priority Review Voucher and was granted Regenerative Medicine Advanced Therapy and Fast Track designations. Ultragenyx must complete confirmatory trials to verify clinical benefit.