Ultragenyx Pharmaceutical Faces Class Action Lawsuit

Investors have until April 6, 2026 to apply for lead plaintiff status in case against Ultragenyx

Mar. 14, 2026 at 2:51am

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Kahn Swick & Foti, LLC, a securities litigation law firm, has filed a class action lawsuit against Ultragenyx Pharmaceutical Inc. on behalf of investors who suffered losses between August 3, 2023 and December 26, 2025. The lawsuit alleges securities fraud related to the company's failed Phase 3 trials for its drug setrusumab (UX143) in treating osteogenesis imperfecta.

Why it matters

This lawsuit highlights the risks investors face when investing in pharmaceutical companies, especially when it comes to the success or failure of clinical trials for new drug candidates. The significant drop in Ultragenyx's stock price following the failed trials underscores the potential financial impact on investors.

The details

On December 26, 2025, Ultragenyx announced that its Phase 3 Orbit and Cosmic studies for setrusumab (UX143) failed to demonstrate a statistically significant reduction in annualized fracture rates for patients with osteogenesis imperfecta. As a result, the company said it would be implementing significant expense reductions. This news caused Ultragenyx's stock price to drop approximately 42% from $34.19 per share on December 26, 2025 to $19.72 per share on December 29, 2025.

  • The class action lawsuit covers the period from August 3, 2023 to December 26, 2025.
  • Investors have until April 6, 2026 to apply for lead plaintiff status in the case.

The players

Kahn Swick & Foti, LLC

A securities litigation law firm that has filed the class action lawsuit against Ultragenyx Pharmaceutical Inc.

Charles C. Foti, Jr.

The former Attorney General of Louisiana and a partner at Kahn Swick & Foti, LLC.

Ultragenyx Pharmaceutical Inc.

A biopharmaceutical company that develops and commercializes novel products for the treatment of rare and ultra-rare genetic diseases.

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What they’re saying

“Ultragenyx investors should contact KSF Managing Partner Lewis Kahn toll-free at 1-877-515-1850 or via email (lewis.kahn@ksfcounsel.com), or visit https://www.ksfcounsel.com/cases/nasdaqgs-rare/ to learn more.”

— Lewis Kahn, Managing Partner, Kahn Swick & Foti, LLC

What’s next

The judge in the case will decide on April 6, 2026 whether to appoint a lead plaintiff for the class action lawsuit.

The takeaway

This lawsuit serves as a reminder for investors to thoroughly research and understand the risks associated with investing in pharmaceutical companies, especially those with drug candidates in clinical trials. The potential for significant stock price volatility underscores the importance of diversification and careful risk management when investing in the biotech sector.