Source

Ultragenyx's pivotal Phase 3 Aspire study of apazunersen (GTX-102) in Angelman syndrome missed both its primary endpoint (change from baseline in Bayley-4 cognitive raw score) and its key secondary endpoint (Multidomain Responder Index net response), with no meaningful separation from placebo. Shares closed down 44.0% on 11.6x average volume — the single largest move on the 2026-09-03 board, and the only one of the day's top movers with no cohort explanation: IBB closed flat (0.0%, 17 of 37 up) and the broad biotech lane -0.1%, so this was idiosyncratic single-asset risk repricing, not a sector event. Sell-side reset immediately: Baird to Neutral from Outperform with the target cut $40 to $16, RBC Capital to Sector Perform from Outperform at $19, Wells Fargo to Equal Weight from Overweight with the target cut $50 to $18. The desk's own news pull ran clean at 20:41 PT and surfaced nothing newer than 2026-09-01 — the catalyst was found by an explicit search, not by the daily pull, which is the coverage gap worth noting.

Takeaway

Ultragenyx's pivotal Phase 3 Aspire study of apazunersen (GTX-102) in Angelman syndrome missed both its primary endpoint (change from baseline in Bayley-4 cognitive raw score) and its key secondary endpoint (Multidomain Responder Index net response), with no meaningful separation from placebo. Shares closed down 44.0% on 11.6x average volume — the single largest move on the 2026-09-03 board, and the only one of the day's top movers with no cohort explanation: IBB closed flat (0.0%, 17 of 37 up) and the broad biotech lane -0.1%, so this was idiosyncratic single-asset risk repricing, not a sector event. Sell-side reset immediately: Baird to Neutral from Outperform with the target cut $40 to $16, RBC Capital to Sector Perform from Outperform at $19, Wells Fargo to Equal Weight from Overweight with the target cut $50 to $18. The desk's own news pull ran clean at 20:41 PT and surfaced nothing newer than 2026-09-01 — the catalyst was found by an explicit search, not by the daily pull, which is the coverage gap worth noting.