Ultragenyx Shares Plunge 44% After Angelman Syndrome Drug Fails Late-Stage Trial

Ultragenyx Pharmaceutical shares cratered roughly 44% on September 3, 2026, after its experimental treatment for Angelman syndrome, a rare neurodevelopmental genetic disorder, failed to meet its primary endpoint in a late-stage clinical trial. The failure was a major blow to one of the company's most closely watched pipeline programs and its biggest growth bets.

The collapse in the stock price triggered a wave of analyst downgrades. Wells Fargo cut Ultragenyx to Equal Weight from Overweight and slashed its price target to $18, while JPMorgan downgraded the stock to Neutral from Overweight with a target of $36. Robert W. Baird moved to Neutral from Outperform with a $16 target, and Evercore ISI cut to In-line from Outperform, also targeting $16.

Despite the setback, some Wall Street analysts have not fully abandoned the stock, pointing to Ultragenyx's growing commercial business as a reason for continued attention. The company is also expected to pursue cost cuts in the wake of the trial failure. Separately, commentator Martin Shkreli publicly argued that Ultragenyx should become a merger and acquisition target following the share price collapse.