Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) announced the publication of 96-week data from its Phase 3 study of GENGLYCOS (pariglasgene brecaparvovec-opnr), an AAV gene therapy for glycogen storage disease type Ia (GSDIa), in The Journal of Inherited Metabolic Disease. The therapy was recently approved by the U.S. Food and Drug Administration for patients aged eight and older with GSDIa.

At Week 96, participants in both the original treatment group and the crossover group achieved a mean reduction in daily cornstarch intake of 61% from baseline while maintaining glycemic control. The study's primary endpoint had previously been met at Week 48, when patients treated with GENGLYCOS showed a mean cornstarch reduction of 41% compared with 10% in the placebo group.

Among participants who required nighttime cornstarch at baseline, 33% of the original GENGLYCOS group and 42% of the crossover group had completely eliminated nighttime cornstarch dosing by Week 96, while maintaining glycemic control.

A patient-centered analysis showed the average cornstarch reduction considered meaningful by participants at baseline was 45%. At Week 48, 83% of GENGLYCOS-treated participants met or exceeded that threshold, with continued improvements through Week 96. At Week 96, 95% of crossover participants and 83% of original treatment participants reported improvement on the Patient Global Impression of Change scale.

The most common treatment-related adverse events were transient elevations in liver enzymes, generally managed with prophylactic corticosteroids. No cases of dorsal root ganglion toxicity, malignancy, or thrombotic microangiopathy were observed through Week 96. Hypertriglyceridemia occurred more frequently in GENGLYCOS-treated participants.

GENGLYCOS holds accelerated FDA approval, and continued approval may depend on verification of clinical benefit in confirmatory trials. GSDIa affects an estimated 1,500 to 2,500 patients in the U.S. and 6,000 to 8,000 patients worldwide.