Ultragenyx Class Action Lawsuit Deadline
Analysis based on 31 articles · First reported Feb 05, 2026 · Last updated Apr 06, 2026
The market is negatively impacted by the significant drop in Ultragenyx's stock price due to the failure of its Phase III clinical trials. This event highlights the inherent risks in the biotechnology and pharmaceutical industries, potentially leading to increased scrutiny of clinical trial disclosures and investor confidence in companies with ongoing drug development.
Ultragenyx is facing a class action lawsuit filed by Rosen Law Firm and Kahn Swick & Foti, alleging that the company made false and misleading statements regarding its Phase III Orbit and Cosmic Studies for setrusumab (UX 143) in patients with Osteogenesis Imperfecta. The lawsuit claims that Ultragenyx expressed confidence in setrusumab's ability to decrease annualized fracture rates and in the study designs, while concealing that the increase in bone density did not correlate with a decrease in fracture rates. On December 26, 2025, Ultragenyx announced that both studies failed to demonstrate a statistically significant reduction in annualized fracture rates, causing its shares to fall approximately 42%. Investors who purchased Ultragenyx common stock between August 3, 2023, and December 26, 2025, have until April 6, 2026, to apply to be lead plaintiff in the lawsuit.
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