August 19, 2026——The U.S. Food and Drug Administration today granted accelerated approval to Genglycos (pariglasgene brecaparvovec-opnr) for reducing daily cornstarch intake as an adjunct to nutritional management in 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 the enzyme glucose-6-phosphatase (G6PC), which prevents the body from converting stored glycogen into glucose. Without this enzyme, patients experience dangerously low blood sugar during fasting. Current standard of care requires strict, lifelong dietary management including frequent meals and round-the-clock cornstarch supplementation.
Genglycos is a one-time AAV8-based gene therapy designed to deliver a functional G6PC gene to the liver, restoring the deficient enzyme and helping maintain stable blood sugar levels.
Clinical Evidence
The accelerated approval is based on a randomized, double-blind, placebo-controlled study in GSDIa patients followed for 48 weeks after dosing. The primary endpoint showed that patients treated with Genglycos achieved a statistically significant mean reduction in daily cornstarch intake of 31% compared to placebo. The secondary endpoint showed a mean reduction of one cornstarch dose per day versus placebo.
Reducing cornstarch intake serves as the surrogate endpoint. The manufacturer must complete additional clinical trials to confirm clinical benefit.
Safety Profile
Serious adverse reactions in Genglycos-treated patients across two studies included anaphylaxis, adrenal insufficiency, high lactate levels, and hypoglycemia. Common adverse reactions included elevated liver enzymes, nausea, headache, constipation, and hyperglycemia. Hypertriglyceridemia occurred in 29% of treated patients versus 8% receiving placebo. Prescribing information carries warnings for anaphylaxis, liver toxicity, adrenal insufficiency, and tumorigenicity risk. Genglycos should not be used during pregnancy.
Regulatory Details
The application received a Rare Pediatric Disease Priority Review Voucher and was granted Regenerative Medicine Advanced Therapy (RMAT) and Fast Track designations.
"This approval is a great milestone in using gene therapy to treat this disease and improve quality of life," said Karim Mikhail, Acting Director of CBER.
"Genglycos offers patients and their families a one-time therapy that targets the root cause of the disease," added Dr. Megha Kaushal, Acting Deputy Director of CBER's Office of Therapeutic Products.
The accelerated approval was granted to Ultragenyx Pharmaceutical, Inc. Continued approval may depend on verification of clinical benefit in confirmatory trials.
