Ultragenyx Pharmaceutical Faces Fraud Lawsuit

The class action lawsuit centers on setrusumab, an antibody treatment for osteogenesis imperfecta (OI), a genetic disorder that results in brittle bones. The legal filings allege that Ultragenyx made false or misleading statements about the drug's effectiveness in its Phase III Orbit and Cosmic studies. Specifically, the lawsuit claims that Ultragenyx created a false impression of setrusumab's potential, minimizing the risk that the clinical trials would fail to show a significant reduction in fracture rates. This optimism was allegedly based on Phase II trial results that lacked a placebo control group for proper comparison. On July 9, 2025, the company announced that the Phase III Orbit study was proceeding to a final analysis at the end of the year, causing an initial stock drop of over 25%. Then, on December 29, 2025, Ultragenyx revealed that both the Orbit and Cosmic studies failed to meet their primary endpoints of reducing fracture rates compared to a placebo or other treatments. Following the December announcement, Ultragenyx's stock price plummeted by more than 42%. The company's CEO, Emil Kakkis, expressed surprise and disappointment at the results, particularly given the promising data from the earlier Phase 2 study. While the trials did not show a statistically significant reduction in fractures, they did demonstrate a significant improvement in bone mineral density, a secondary goal of the studies. Ultragenyx has stated it will implement significant expense reductions in light of the trial failures. Multiple law firms, including Kessler Topaz Meltzer & Check, LLP, Bronstein, Gewirtz & Grossman, LLC, and Rosen Law Firm, have filed lawsuits on behalf of investors. The case is captioned Bailey v. Ultragenyx Pharmaceutical Inc., No. 26-cv-01097, in the Northern District of California. Investors who purchased stock between August 3, 2023, and December 26, 2025, have until April 6, 2026, to seek lead plaintiff status.