Ultragenyx Pharmaceutical Hit With Class Action Lawsuit

The class action lawsuit against Ultragenyx Pharmaceutical alleges the company made materially false and misleading statements concerning the potential of its drug, setrusumab. The drug was being investigated as a treatment for Osteogenesis Imperfecta, a genetic disorder characterized by brittle bones. The core of the allegations centers on the company's "overwhelmingly positive statements" to investors about the drug's prospects. These statements were allegedly made despite underlying risks in the clinical trial protocols. The lawsuit claims that while setrusumab did show an increase in bone mineral density, the company failed to disclose that this did not necessarily correlate to a decrease in fracture rates. The plaintiffs argue that the Phase III Orbit and Cosmic studies were less likely to demonstrate this link than the company's optimistic communications suggested. A key point in the complaint is that Ultragenyx's optimism was based on Phase II study results that lacked a placebo control group for a direct comparison. This omission, the lawsuit contends, meant that a reduction in the annualized fracture rate could have been due to an increased standard of care or a placebo effect, a risk not conveyed to investors. For instance, a June 2024 press release highlighted "sustained reductions in fracture rates" and "ongoing and meaningful improvements in lumbar spine bone mineral density" from the Phase 2 data. The situation came to a head on December 29, 2025, when Ultragenyx announced that both the Phase III Orbit and Cosmic studies failed to meet their primary endpoints of statistically significant reductions in the annualized clinical fracture rate. The company's CEO, Emil Kakkis, expressed surprise and disappointment at the results. Following this announcement, Ultragenyx's stock price experienced a sharp decline. On December 26, 2025, the stock closed at $34.19 per share. By December 29, 2025, it had fallen to $19.72 per share, a drop of approximately 42.32%. Multiple law firms, including Kessler Topaz Meltzer & Check, The Gross Law Firm, Rosen Law Firm, and Robbins Geller Rudman & Dowd LLP, have filed class-action lawsuits on behalf of investors. The deadline for investors to seek lead plaintiff status is April 6, 2026. The case is filed in the United States District Court for the Northern District of California.