Genglycos (pariglasgene brecaparvovec-opnr): FDA approval, pivotal trial and safety
Approved
Type
Gene therapy · Intravenous
FDA-approved use
To reduce daily cornstarch intake as an adjunct to nutritional management in adult and pediatric patients 8 years of age and older with glycogen storage disease type Ia (GSDIa)Wording from FDA's list of novel approvals.
Company
Ultragenyx
Application
BLA 125858
Specialty
Genetics
At a glance
Genglycos (pariglasgene brecaparvovec-opnr) is an AAV8-based gene therapy approved in August 2026 under accelerated approval to reduce daily cornstarch intake, as an adjunct to nutritional management, in patients 8 years and older with glycogen storage disease type Ia. Approval rests on reduction in daily cornstarch intake in a randomized, placebo-controlled trial; the sources provided do not give the effect size. The main safety points are immune-mediated liver enzyme elevation, hypersensitivity and infusion reactions, and adrenal insufficiency.
What it is and how it works
Genglycos delivers a working copy of the glucose-6-phosphatase gene to liver cells with a single intravenous infusion. The gene is under its native human promoter and enhancer. The aim is for hepatocytes to make normally functioning enzyme. Standard care manages the metabolic defect with strict diet and cornstarch, and does not address the underlying enzyme deficiency.
Multicenter, randomized, double-blind, placebo-controlled for 48 weeks, then crossover to week 96. Patients first completed a 16-week nutritional optimization and stabilization period.
Patients
49 randomized 1:1; 46 treated and analyzed. Mean age 20.5 years (range 8 to 37). 58.7% male. Patients with detectable baseline anti-AAV8 antibodies were excluded.
Compared with
Placebo
Primary endpoint
Percent change from baseline to Week 48 in total daily cornstarch intake in grams.
Result
The sources provided do not report the primary result, effect size, or P value.
Other results
Secondary end points included change in the number of daily cornstarch doses and the percent of glucose values in the hypoglycemic range. Results are not given in the sources provided.
Safety in the trial
In the 48-week period, 21 patients received Genglycos and 25 placebo. Seven serious adverse events occurred: anaphylaxis or infusion reaction (2), adrenal insufficiency (2), high lactate (2), and hypoglycemia (1). ALT/AST elevation occurred in 71% with Genglycos vs 12% with placebo. It was mostly mild to moderate, with one severe asymptomatic event, and resolved within 15 weeks. Nausea occurred in 38% vs 16%, headache 24% vs 12%, hypertriglyceridemia 29% vs 8%, and adrenal insufficiency 24% vs 0.
How does Genglycos (pariglasgene brecaparvovec-opnr) compare with the alternatives (Uncooked cornstarch therapy, Continuous overnight gastric feeding, Dietary management) for its approved use (to reduce daily cornstarch intake as an adjunct to nutritional management in adult and pediatric patients 8 years of age and older with glycogen storage disease type Ia (GSDIa))? Summarize head-to-head and indirect evidence, efficacy, safety and where each fits, with citations.
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Safety signals
There is no boxed warning. Hypersensitivity reactions, including anaphylaxis, and infusion reactions can occur. Premedication and monitoring during and after infusion are advised. Immune-mediated hepatotoxicity with raised ALT and AST occurs, so the label advises avoiding use in preexisting hepatic impairment or acute hepatic viral infection and monitoring liver tests for the first 6 months. Adrenal insufficiency occurred, with two serious cases in the placebo-controlled period, and needs monitoring during and after corticosteroid therapy and tapering. A theoretical risk of tumorigenicity from vector integration exists. The most common adverse reactions were increased transaminases and nausea.
What it competes with
GSDIa is managed with strict dietary therapy to maintain normal glucose, centered on frequent cornstarch dosing. Adherence is hard, and long-term complications can still occur despite good metabolic control.
Uncooked cornstarch therapyMainstay of dietary management, given at scheduled intervals to maintain blood glucose, including overnight.
Continuous overnight gastric feedingAlternative to overnight cornstarch for sustaining glucose, but needs a feeding tube and pump.
Dietary managementFrequent meals with restricted fructose, sucrose, and lactose. Does not address the underlying enzyme deficiency.
Bottom line for clinicians
Genglycos is for patients 8 years and older with GSDIa who want to lessen their cornstarch burden. It is not a replacement for nutritional management. Weigh liver toxicity, adrenal insufficiency, infusion reactions, and a corticosteroid course against the benefit. Because approval is accelerated, clinical benefit still needs confirmation. Patients with baseline anti-AAV8 antibodies were excluded from the trial.
Dosing, contraindications and full warnings are in the prescribing information.
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Last updated October 28, 2026 by 2 Minute Medicine.
For healthcare professionals. A summary of public FDA documents and published trials, not medical advice. Check the full prescribing information before prescribing.
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