Ultragenyx Hit With Securities Class Action Over Failed Phase III Trials

Overview

• Pomerantz LLP announced a securities class action against Ultragenyx and is soliciting shareholders to seek the lead plaintiff role by April 6, 2026.
• Rosen Law Firm also issued a notice, citing a class period from August 3, 2023 through December 26, 2025 for purchasers of Ultragenyx common stock.
• The suit centers on statements about setrusumab (UX143) and the Phase III Orbit and Cosmic studies, alleging the company overstated the drug’s chances of cutting fracture rates and downplayed risks in the study designs.
• Ultragenyx disclosed on December 29, 2025 that both trials missed their main goals, and the stock fell 42% to close at $34.19 that day, after an earlier 25% drop in July 2025 following an Orbit study update.
• No class has been certified and the merits have not been decided, so the near-term step is the court’s selection of a lead plaintiff, a routine stage in biotech investor suits that often follow adverse clinical results.