Ultragenyx Pharmaceutical Faces Investor Lawsuit
A securities fraud class-action lawsuit has been filed against Ultragenyx Pharmaceutical Inc. (RARE). The lawsuit, brought by Kessler Topaz Meltzer & Check, LLP, seeks to recover losses for investors who purchased stock between August 2023 and December 2025.
The lawsuit centers on allegations that Ultragenyx made false and misleading statements about the potential of its drug, setrusumab (UX143). This drug was being investigated as a treatment for osteogenesis imperfecta, a genetic disorder characterized by brittle bones. The core of the investors' complaint is that the company misrepresented the efficacy of setrusumab. The lawsuit claims Ultragenyx created a false impression of reliable data regarding the drug's effect on patients and downplayed the risks of the clinical trials failing. Specifically, the suit alleges that Ultragenyx based its optimistic outlook on Phase II results that lacked a placebo control group. This omission, the plaintiffs argue, made it impossible to rule out that any observed reduction in fracture rates was due to a placebo effect or an increased standard of care. The negative news broke on December 29, 2025, when Ultragenyx announced that its Phase III Orbit and Cosmic studies of setrusumab failed to show a statistically significant reduction in fracture rates. Following this announcement, the company's stock price plummeted by over 42%, falling from a closing price of $34.19 on December 26, 2025, to $19.72 on December 29, 2025. The class action, titled *Steven Bailey v. Ultragenyx Pharmaceutical Inc., et al.*, was filed in the United States District Court for the Northern District of California. Investors who purchased the stock during the specified period have until April 6, 2026, to file to be the lead plaintiff.
