Ultragenyx Faces Lawsuit Over Alleged Securities Fraud

Investors claim company misled them about clinical trial results for rare disease drug

Published on Feb. 10, 2026

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A class action lawsuit has been filed against Ultragenyx Pharmaceutical Inc. on behalf of investors who purchased the company's common stock between August 3, 2023 and December 26, 2025. The lawsuit alleges that Ultragenyx misled investors by concealing that its ORBIT and COSMIC studies, which tested setrusumab as a treatment for Osteogenesis Imperfecta, did not significantly reduce clinical fracture rates compared to control groups. Following the disclosure of this information, Ultragenyx's stock price plummeted by over 42% in a single day.

Why it matters

The lawsuit highlights the importance of transparency and accurate disclosures for publicly traded pharmaceutical companies, especially those working on treatments for rare diseases. Investors rely on this information to make informed decisions, and allegations of securities fraud can severely damage a company's reputation and stock price.

The details

According to the complaint, while Ultragenyx was publicly raising investor expectations about the ORBIT and COSMIC studies, the company allegedly concealed that the studies did not significantly reduce clinical fracture rates compared to control groups. This information was only disclosed later, leading to a sharp drop in Ultragenyx's stock price.

  • The class period covers August 3, 2023 through December 26, 2025.
  • Ultragenyx's stock price dropped from $34.19 on December 26, 2025 to $19.72 per share on December 29, 2025, a decline of over 42%.

The players

Ultragenyx Pharmaceutical Inc.

A biopharmaceutical company specializing in treatments for rare diseases, headquartered in Novato, California.

Berger Montague PC

A national plaintiffs' law firm that has filed the class action lawsuit against Ultragenyx on behalf of investors.

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What’s next

The judge will decide by April 6, 2026 whether to appoint a lead plaintiff to represent the class of investors in the lawsuit against Ultragenyx.

The takeaway

This case highlights the importance of pharmaceutical companies providing accurate and transparent information to investors, especially regarding the results of clinical trials for rare disease treatments. Allegations of securities fraud can have severe consequences for a company's stock price and reputation.