Ultragenyx Announces Positive Longer-term Data from Phase 3 Study of DTX401 AAV Gene Therapy for the Treatment of Glycogen Storage Disease Type Ia (GSDIa)

Core Insights - Ultragenyx Pharmaceutical Inc. announced positive long-term results from its Phase 3 study of DTX401, a gene therapy for glycogen storage disease type Ia (GSDIa), showing significant reductions in daily cornstarch intake while maintaining glycemic control [2][4][10] Group 1: Study Results - At Week 48, patients treated with DTX401 (n=20) experienced a mean reduction in cornstarch intake of 41% compared to a 10% reduction in the placebo group (n=24) [4] - By Week 96, the DTX401 group achieved a mean reduction in daily cornstarch intake of 61% from baseline, with the crossover group achieving similar results [4][5] - Participants in the DTX401 group saw a 70% reduction in nighttime cornstarch intake, with two-thirds eliminating at least one nighttime dose [5] Group 2: Glycemic Control and Quality of Life - Participants maintained low levels of hypoglycemia and improved euglycemia (70-120 mg/dL) throughout the study despite substantial reductions in cornstarch intake [5][7] - 83% of the DTX401 group and 95% of the crossover group reported improvements in disease burden as measured by the Patient Global Impression of Change (PGIC) [7] - Interviews indicated that participants reported less hypoglycemia and fatigue, with significant improvements in physical, social, and daily regimen impacts [8] Group 3: Safety Profile - DTX401 demonstrated an acceptable safety profile consistent with Phase 1/2 study results, with manageable hepatic reactions and no serious adverse events reported [9][10] - Hypertriglyceridemia was observed in all study groups but was more frequent following DTX401 treatment [9] Group 4: Background Information - GSDIa is a rare and life-threatening disease caused by a deficiency of the G6Pase enzyme, leading to severe hypoglycemia and excess hepatic glycogen storage [13] - DTX401 is an investigational AAV8 gene therapy designed to improve G6Pase activity and reduce hepatic glycogen levels, addressing a significant unmet medical need [12][13]