FDA Approves Ultragenyx’s GENGLYCOS™ Gene Therapy for GSDIa

On August 19, 2026, Ultragenyx Pharmaceutical announced that the FDA granted accelerated approval to its GENGLYCOS (pariglasgene brecaparvovec-opnr) for patients eight years and older with glycogen storage disease type Ia (GSDIa). The therapy is approved to reduce daily cornstarch intake as an adjunct to nutritional management. It is the first FDA-approved treatment for GSDIa and Ultragenyx’s first approved gene therapy.

GSDIa is a rare genetic disorder that prevents the liver from properly releasing glucose, placing patients at risk of severe hypoglycemia. Management typically requires frequent raw cornstarch intake and strict dietary monitoring.

The approval was based on the Phase 3 GlucoGene study, in which GENGLYCOS significantly reduced cornstarch requirements compared with placebo. Because the therapy received accelerated approval, continued approval may depend on confirmation of clinical benefit through post-marketing studies. Ultragenyx also received a Priority Review Voucher.

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