Genglycos Approved for Glycogen Storage Disease Type 1a
On Aug. 19, 2026, the US Food and Drug Administration (FDA) granted accelerated approval to Genglycos™ (pariglasgene brecaparvovec-opnr – Ultragenyx Pharmaceuticals), an adeno-associated vector (AAV)8 liver-directed gene therapy, to reduce daily cornstarch intake as an adjunct to nutritional management in adults and pediatric patients eight years of age and older who have glycogen storage disease type Ia (GSDIa). It is the first approved therapy targeting the underlying cause of this ultra-rare disease by delivering a functional copy of the G6PC gene. Approval was based on the surrogate endpoint of reduced cornstarch intake and continued approval may be contingent on verification of clinical benefit in confirmatory trials. The recommended dose is a single one-time intravenous (IV) infusion of 1.0 × 10¹³ genome copies (gc)/kg body weight. Patients receive acetaminophen and non-sedating antihistamines 30 to 60 minutes before infusion. Prophylactic corticosteroids begin two weeks after administration and continue for at least eight weeks. Genglycos will launch at qualified treatment centers within the next 30 to 60 days, with a list price of $2.7 million. For complete prescribing information, see here.
At a Glance
- Brand Drug: Genglycos™ (pariglasgene brecaparvovec-opnr); formerly DTX401
- Manufacturer: Ultragenyx Pharmaceuticals
- Date Approved: Aug. 19, 2026
- Indication: To reduce daily cornstarch intake as an adjunct to nutritional management in adults and pediatric patients eight years of age and older who have GSDIa.
- Dosage Forms Available: Suspension for IV infusion, 3.0 × 10¹³ gc/mL; kit of 3–15 single-dose vials based on body weight
- Launch Date: Within the next 30 to 60 days
- Estimated Annual Cost: $2.7 million for the one-time infusion
- FDA Designations: Accelerated Approval, Rare Pediatric Disease Priority Review Voucher, Orphan Drug, Fast Track, and Regenerative Medicine Advanced Therapy (RMAT).
- GSDIa is an ultra-rare, inherited metabolic disorder caused by G6PC gene mutations resulting in deficiency of glucose-6-phosphatase, the liver enzyme that releases stored glucose into the bloodstream. Patients experience dangerously low blood sugar during fasting, risking seizures and life-threatening hypoglycemia, plus long-term metabolic complications.
- Standard of care is a burdensome, around-the-clock regimen of raw/uncooked cornstarch as oral glucose replacement therapy. Genglycos is the only approved therapy for GSDIa.
- GSDIa affects an estimated 1,500–2,500 people in the US.
- Approval was based on a statistically significant reduction in daily cornstarch requirements versus placebo (p<0.001). Mean reductions in daily cornstarch intake deepened over time, from approximately 41% at week 48 to 60–61% at week 96, while patients maintained euglycemia, low hypoglycemia and improved fasting tolerance and quality of life.
- The prescribing information includes warnings for hypersensitivity/infusion reactions (including anaphylaxis), hepatotoxicity (monitor transaminases for greater than or equal to six months), adrenal insufficiency related to corticosteroid therapy, and a theoretical tumorigenicity risk from AAV vector integration.
- The most common adverse effects were increased transaminase levels and nausea.
- Since approval was granted under accelerated approval based on a surrogate endpoint (reduction in daily cornstarch intake), continued approval is contingent upon verification of clinical benefit in required confirmatory and post-marketing studies, including two years of data from 50 treated and 20 control patients via a 10-year Disease Monitoring Program.