Ultragenyx Pharmaceutical has received FDA accelerated approval for GENGLYCOS, a gene therapy for adults and children aged 8 years and older with glycogen storage disease type Ia, or GSDIa.
GENGLYCOS, also known as pariglasgene brecaparvovec-opnr and DTX401, is approved to reduce daily cornstarch intake as an adjunct to nutritional management. Ultragenyx said it is the first FDA-approved therapy designed to address the underlying cause of GSDIa and the company’s first gene therapy approval.
GSDIa is an ultra-rare inherited metabolic disease caused by deficiency of an enzyme needed to release glucose from the liver into the bloodstream. Patients face the risk of severe, potentially life-threatening hypoglycemia and typically require a demanding around-the-clock regimen of raw cornstarch and dietary management. Ultragenyx estimates that 1,500 to 2,500 people in the United States and 6,000 to 8,000 people in commercially accessible geographies worldwide have the condition.
The FDA’s decision was based on the 48-week randomized, double-blind, placebo-controlled Phase 3 GlucoGene study. The trial enrolled 46 participants aged 8 and older and evaluated a 1.0 × 10¹³ GC/kg dose of DTX401 against placebo. In the modified intention-to-treat analysis, the treated group showed a statistically significant reduction in cornstarch requirements, with a p-value below 0.001.
The approval carries post-marketing requirements. Ultragenyx agreed to provide two years of safety and efficacy data from open-label commercial treatment of 50 patients and 20 controls through an expansion of its GSDIa Disease Monitoring Program. The program will follow clinical-trial participants and new commercial patients for up to 10 years.
GENGLYCOS will be administered through a national network of Qualified Treatment Centers. Ultragenyx said it will support patients and caregivers through its UltraCare program, including dedicated gene therapy guides to help navigate insurance coverage and treatment access.
The therapy is manufactured at Ultragenyx’s gene therapy manufacturing facility in Bedford, Massachusetts. The company also received a Priority Review Voucher upon approval.
GENGLYCOS is contraindicated in patients with known severe hepatic fibrosis or cirrhosis. The treatment carries warnings for hypersensitivity and infusion reactions, immune-mediated liver toxicity, adrenal insufficiency during corticosteroid use or tapering, and a theoretical risk of tumorigenicity associated with AAV vector DNA integration.
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