Ultragenyx Shares Plunge After Angelman Syndrome Drug Fails Pivotal Phase 3 Trial

Shares of Ultragenyx Pharmaceutical Inc. (RARE) plummeted in pre-market trading Thursday after the company announced its pivotal Phase 3 Aspire study for apazunersen in Angelman syndrome did not meet its goals. The stock fell by as much as 44.7% to $14.67, hitting levels not seen in over a year.

Pivotal Trial Misses Endpoints

The company disclosed late Wednesday that the study of apazunersen, also known as GTX-102, failed to meet its primary endpoint, which was the change from baseline in the Bayley-4 cognitive raw score. The trial also missed its key secondary endpoint, the net response in the Multidomain Responder Index.

According to the company, investigators found no meaningful differences between the patient group treated with apazunersen and the placebo group on either measure. The outcome represents a significant clinical setback for a drug that was considered a cornerstone of the company's development pipeline for a rare disease with substantial unmet medical need.

Analysts Downgrade Stock, Slash Targets

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The trial failure prompted a cascade of downgrades from Wall Street analysts on Thursday morning as they reassessed the company's future prospects. The actions reflected a swift loss of confidence in a key asset.

• Evercore ISI downgraded the stock to In Line from Outperform and cut its price target to $16 from $34.
• Baird moved its rating to Neutral from Outperform, lowering its target to $16 from $40.
• JPMorgan lowered its rating to Neutral from Overweight, reducing its price target to $36 from $80.
• William Blair downgraded shares to Market Perform, noting it was removing the GTX-102 pipeline contribution from its valuation entirely.

Investor Outlook and Context

Analysts at William Blair highlighted additional headwinds for Ultragenyx beyond the trial failure, flagging the company's ongoing cash consumption and the longer-term risk of its key drug, Crysvita, losing market exclusivity. The sharp sell-off pushed the stock price well below its previous 52-week low of $18.29, reflecting the market's reassessment of the company's value without the potential blockbuster revenue from apazunersen.