What the FDA decided on Genglycos for Glycogen storage disease type 1a
The FDA approved Genglycos (pariglasgene brecaparvovec) for glycogen storage disease type 1a.
Accelerated approval for an AAV8 gene therapy, for patients 8 and older, to reduce daily cornstarch intake as an add-on to nutritional management.
Who the Genglycos decision matters to
Glycogen storage disease type Ia (GSD Ia, von Gierke disease) is an inherited condition in which the liver cannot release sugar into the blood between meals, so blood sugar drops dangerously low without frequent feeding and glycogen and fat build up in the liver and kidneys.
Prevalence: About 1 in 100,000 births for glycogen storage disease type I overall, with type Ia making up about 80% (NORD; MedlinePlus Genetics); about 1 in 20,000 among people of Ashkenazi Jewish descent. See our full Glycogen Storage Disease Type Ia page for current treatments, recruiting trials, and community resources.
How Genglycos works
Genglycos: one-time AAV8 gene therapy that delivers a working copy of the G6PC gene to liver cells so they can make the glucose-6-phosphatase enzyme. Our full Genglycos profile covers how it works, side effects in plain language, and its trial history.
Where Glycogen Storage Disease Type Ia treatment stands today
Read our full Glycogen Storage Disease Type Ia treatment summary
The FDA gave accelerated approval on August 19, 2026 to Genglycos (pariglasgene brecaparvovec), Ultragenyx's one-time gene therapy infusion, for people 8 and older with GSD Ia. It is approved to reduce daily cornstarch alongside nutrition therapy: in the GlucoGene Phase 3 trial (NCT05139316) daily cornstarch fell 41.1% on Genglycos against 10.2% on placebo over 48 weeks.
People cannot have antibodies to the AAV8 virus shell it uses, need steroids for at least 8 weeks, and should not have liver scarring; liver enzyme rises occurred in 71% against 12% on placebo. Other approaches are earlier in testing: Beam Therapeutics' base editor BEAM-301 is in a recruiting Phase 1/2 trial (NCT06735755), and Moderna's mRNA-3745 (NCT05095727) is active but not recruiting.
The Association for Glycogen Storage Disease connects families with specialist clinics.
The Glycogen Storage Disease Type Ia page has every treatment and trial →Meanwhile, 5 Glycogen Storage Disease Type Ia studies are open or about to open
The FDA's decision does not end research on Glycogen Storage Disease Type Ia. Of these, 1 tests a treatment; the others follow patients over time. The most recently updated:
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- Trial Alerts, when a new trial opens or a trial changes
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Frequently asked questions
Has the FDA decided on Genglycos?
The FDA has already decided. It approved the application.
Details: the outcome and what it means are at the top of this page.
Source: Ultragenyx press release
What was Genglycos approved for?
The FDA approved Ultragenyx's BLA for Genglycos in Glycogen storage disease type 1a.
What to know: Accelerated approval for an AAV8 gene therapy, for patients 8 and older, to reduce daily cornstarch intake as an add-on to nutritional management.
How it works: One-time AAV8 gene therapy that delivers a working copy of the G6PC gene to liver cells so they can make the glucose-6-phosphatase enzyme.
More: the Genglycos drug page explains it in plain language.
Is there already an FDA-approved treatment for Glycogen Storage Disease Type Ia?
Yes. Trial Friend's drug list includes 1 FDA-approved drug for Glycogen Storage Disease Type Ia.
Approved: Genglycos (pariglasgene brecaparvovec).
Check: the Glycogen Storage Disease Type Ia page also searches FDA drug labels for approved treatments.
What did the Genglycos trials show?
GlucoGene (NCT05139316), a Phase 3 randomized, double-blind, placebo-controlled trial, treated 46 people (21 on Genglycos, 25 on placebo) for 48 weeks. Daily cornstarch fell 41.1% on Genglycos against 10.2% on placebo, a difference of 30.9 percentage points, about 1.2 fewer cornstarch doses a day against 0.2.
More: the Genglycos drug page has the full trial history and sources.
What are the side effects of Genglycos?
Genglycos has no boxed warning. It must not be given to people with severe liver scarring (fibrosis) or cirrhosis.
Most common: Liver enzyme rises (71% against 12% on placebo), Nausea (38% against 16%), High triglycerides (29% against 8%), Headache (24% against 12%), Adrenal insufficiency (24% against 0%), Acne (19% against 0%).
More: the Genglycos drug page has the label's warnings in full.
How much will Genglycos cost?
Trial Friend does not list a price for Genglycos. What you pay depends on your insurance and on help from the drugmaker or a charity fund.
Find help: the patient assistance finder lists programs by insurance type.
What happens after the Genglycos decision?
The FDA approved Genglycos for Glycogen storage disease type 1a on August 19, 2026.
Next steps: getting the drug still takes time. Specialty pharmacy setup, insurance review and patient assistance often take weeks. Our guide covers what families can do on day 1.
Where this outcome comes from
The outcome on this page comes from Ultragenyx press release. This page rechecks against our calendar, which is re-verified daily.