NOVATO, Calif., May 30, 2024 – Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) today reported successful topline results from the Phase 3 GlucoGene study (NCT05139316) evaluating DTX401, an investigational gene therapy for glycogen storage disease type Ia (GSDIa) in patients aged eight years and older.
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The study achieved its primary endpoint, showing a statistically significant and clinically meaningful reduction in daily cornstarch intake at Week 48. Patients treated with DTX401 experienced a 41.3% reduction in cornstarch intake compared to 10.3% in the placebo group (p<0.0001). All patients in the treatment group reduced their cornstarch intake, with 68% achieving a ≥30% reduction and 37% achieving a ≥50% reduction, compared to 13% and 4%, respectively, in the placebo group.


Key Findings:

  • Reduction in Cornstarch Doses: DTX401 led to a mean reduction of 1.1 cornstarch doses per day, significantly higher than the 0.2 reduction in the placebo group (p=0.0011).
  • Glucose Control: The study demonstrated non-inferiority in glucose control between groups, with significant reductions in cornstarch intake in the treatment group.
  • Patient Global Impression of Change (PGIC): The DTX401 group showed a median score of 2.0 (moderately improved) versus 1.0 (minimally improved) for the placebo group (p=0.132). A ≥30% reduction in cornstarch intake correlated with better PGIC scores.


Safety Profile: The safety profile of DTX401 was consistent with previous studies, with manageable non-serious hepatic effects and no observed AAV8 class effects like dorsal root ganglion toxicity or thrombotic microangiopathy.


Statements from Key Personnel:

  • Eric Crombez, M.D., Chief Medical Officer at Ultragenyx, remarked, “These clinically important and statistically significant results reflect the acquired ability to break down glycogen in treated patients, showcasing the potential of DTX401.”
  • Rebecca Riba-Wolman, M.D., Study Investigator, emphasized, “The reduction in cornstarch intake with maintained glucose control offers significant benefits, improving daily life for GSDIa patients.”


Full 48-week data will be presented at an upcoming scientific conference, and discussions with regulatory authorities are planned to support a marketing application in 2025.

Phase 1/2 Data: Ultragenyx also presented long-term data showing sustained reductions in cornstarch intake, with a mean 72% reduction over five years in patients treated with DTX401.

Conference Call Information: Ultragenyx will host a conference call at 5:00 p.m. ET today to discuss the topline data. The webcast will be available on the company’s website.


About GSDIa and DTX401:

GSDIa is a serious inherited disease caused by a defective gene for the enzyme G6Pase-α, leading to severe hypoglycemia and potential organ damage. DTX401, an AAV8 gene therapy, aims to deliver stable G6Pase-α expression and activity, improving glucose regulation and reducing glycogen accumulation. DTX401 has received multiple designations, including orphan drug and Fast Track, from regulatory agencies.

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