Ultragenyx fails phase 3 Angelman test, plots ‘significant expense reductions’

Live updates

1. 11d ago

   Ultragenyx shares plunge after Phase 3 Angelman syndrome trial failure

   Ultragenyx Pharmaceutical shares dropped between 40.3% and 44% in early September 2026 after its Phase 3 Aspire trial for apazunersen (GTX-102) failed. The drug, an antisense oligonucleotide designed to treat the rare Angelman syndrome, did not meet its primary or key secondary cognitive and functional endpoints. In response to the failure, the company is planning "significant expense reductions" and a review of the program. Despite the setback, the FDA confirmed that Ultragenyx's recently approved GENGLYCOS gene therapy for glycogen storage disease type Ia qualifies for a rare pediatric disease priority review voucher.

   Why it matters

   Angelman syndrome is a rare disease that requires specialized therapeutic interventions. The failure of GTX-102 removes a key late-stage candidate from the company's pipeline, impacting investor confidence. Analysts are now focusing on the company's remaining commercial pipeline to determine the stock's value.

   What is confirmed

   • The Phase 3 Aspire trial of apazunersen (GTX-102) failed to meet primary and key secondary cognitive and functional endpoints.
   • Ultragenyx is planning "significant expense reductions" following the trial failure.
   • The company's stock price fell by more than 40% in early September 2026.
   • The FDA confirmed that GENGLYCOS gene therapy for glycogen storage disease type Ia qualifies for a rare pediatric disease priority review voucher.

   What to watch next

   • Specific details and scale of the planned expense reductions
   • Updates on the status of the GTX-102 program review
   • Impact of the rare pediatric disease priority review voucher on future filings
   Sources used for this update (8)

   1. Fierce Biotech — Ultragenyx fails phase 3 Angelman test, plots ‘significant expense reductions’
   2. STAT — Ultragenyx drug to treat Angelman syndrome, a rare disease, fails late-stage trial
   3. Barron's — Is Ultragenyx Stock a Buy After GTX-102 Flop? Analysts Point to Commercial Pipeline
   4. FirstWord Pharma — Ultragenyx's ASO fails in Angelman syndrome, triggering sell-off
   5. BioPharma Dive — Ultragenyx to weigh ‘significant’ cost cuts as Angelman drug fails key study
   6. Investor's Business Daily — 'Fall From Grace' — Biotech Crashes 44% To A Record Low
   7. finance.yahoo.com — Why Ultragenyx Pharmaceutical (RARE) Is Down 40.3% After Angelman Trial Failure And Cost-Cut Plan
   8. 247wallst.com — Ultragenyx Pharmaceutical Inc
   confidence 100%