Ultragenyx lands FDA approval for GENGLYCOS, first gene therapy for glycogen storage disease type Ia

Ultragenyx Pharmaceutical has received US FDA accelerated approval for GENGLYCOS , the first-ever therapy designed to treat the underlying cause of glycogen storage disease type Ia (GSDIa), the company announced on 19 August 2026.

GSDIa is a rare, inherited metabolic disorder caused by deficiency of the glucose-6-phosphatase enzyme, leaving patients unable to properly regulate blood sugar and prone to life-threatening hypoglycaemia. GENGLYCOS is an AAV-based gene therapy delivering a functional copy of the affected gene, offering a one-time approach in place of the strict dietary and glucose-management regimens patients rely on today.

The clearance is Ultragenyx's first gene therapy approval and its fifth FDA approval overall, marking a milestone for a company built around rare and ultra-rare genetic diseases. As an accelerated approval, it will be supported by confirmatory data.

Source: Ultragenyx, 19 August 2026.