Ultragenyx's gene therapy DTX401 for Glycogen Storage Disease Type Ia (GSDIa) has demonstrated sustained efficacy over 96 weeks, with patients showing significant reductions in daily cornstarch intake.

Patients treated with DTX401 experienced a 61% decrease in total daily cornstarch consumption at 96 weeks, including a 70% reduction at night, indicating improved metabolic control.

Most patients were able to further decrease or eliminate nighttime cornstarch doses, reflecting better liver glycogen breakdown and glucose production during fasting or stress.

Throughout the second year, hypoglycemia remained low, with improved euglycemic levels and protection against severe hypoglycemia, showing sustained glucose regulation.

Patients reported functional improvements in physical, social, and dietary aspects, with 83% in the DTX401 group and 95% in the crossover group noting reduced disease burden at 96 weeks.

An additional Japanese cohort of three pediatric patients showed a 95% reduction in cornstarch intake at 24 weeks, with two patients stopping cornstarch entirely and demonstrating better glycemic control.

The safety profile of DTX401 was acceptable, with no new adverse effects such as dorsal root ganglion toxicity, malignancy, or microangiopathy; hepatic reactions were manageable with corticosteroids.

Hypertriglyceridemia was observed across all groups, more frequently in DTX401-treated patients, consistent with known effects of gene therapy.

Ultragenyx has initiated a rolling Biologics License Application (BLA) submission to the FDA for DTX401, supported by 96-week data, with full submission expected in the fourth quarter of 2025.