Ultragenyx Pharmaceutical Faces Lawsuit

The lawsuit centers on setrusumab, an antibody treatment for Osteogenesis Imperfecta (OI), a genetic disorder characterized by brittle bones. The complaint alleges that Ultragenyx made overly positive statements about the drug's ability to reduce fracture rates in patients. At the heart of the matter are the Phase III Orbit and Cosmic clinical trials. The suit claims the company downplayed the risk that these studies would fail to show a statistically significant reduction in the annualized fracture rate. A key allegation is that Ultragenyx based its optimistic projections on Phase II study results that lacked a placebo control group for comparison. This omission, the lawsuit argues, meant that any observed reduction in fractures could have been due to an increased standard of care or a placebo effect rather than the drug itself. The company's stock price took a significant hit on two separate occasions following negative announcements about the trials. On July 9, 2025, the stock fell over 25% after it was revealed that the Phase III Orbit study's second interim analysis did not achieve statistical significance. A more substantial drop of over 42% occurred after a December 29, 2025, announcement that both the Orbit and Cosmic studies had failed to meet their primary endpoints. The stock price fell from $34.19 on December 26, 2025, to $19.72 on December 29, 2025. The class action, filed in the Northern District of California, seeks to recover damages for investors who purchased Ultragenyx common stock between August 3, 2023, and December 26, 2025. Several law firms, including Kessler Topaz Meltzer & Check and Robbins Geller Rudman & Dowd, are representing the plaintiffs. The deadline for investors to seek lead plaintiff status is April 6, 2026.