Ultragenyx Pharmaceutical Faces Class Action Lawsuit Deadline

Investors have until April 6, 2026 to apply for lead plaintiff role in case against the pharmaceutical company.

Published on Feb. 5, 2026

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Kahn Swick & Foti, LLC ('KSF') and KSF partner, former Attorney General of Louisiana, Charles C. Foti, Jr., have notified investors in Ultragenyx Pharmaceutical Inc. ('Ultragenyx') of a class action securities lawsuit. The lawsuit seeks to recover losses on behalf of investors who were adversely affected by alleged securities fraud between August 3, 2023 and December 26, 2025.

Why it matters

The lawsuit against Ultragenyx comes after the company announced in December 2025 that its Phase III Orbit and Cosmic studies for the drug setrusumab (UX143) failed to demonstrate a statistically significant reduction in annualized fracture rates for patients with osteogenesis imperfecta. This news caused Ultragenyx's stock price to plummet by 42%.

The details

The class action lawsuit, titled 'Steven Bailey v. Ultragenyx Pharmaceutical Inc., et al., No. 26-cv-01097', alleges that Ultragenyx made false and misleading statements about the efficacy of setrusumab during the class period. Investors who suffered losses during this time have until April 6, 2026 to apply to be the lead plaintiff in the case, although they do not need to serve as lead plaintiff to share in any potential recovery.

  • The class period for the lawsuit is from August 3, 2023 to December 26, 2025.
  • Ultragenyx announced the failed Phase III studies on December 26, 2025.
  • The application deadline for investors to become the lead plaintiff is April 6, 2026.

The players

Ultragenyx Pharmaceutical Inc.

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

Kahn Swick & Foti, LLC (KSF)

A boutique securities litigation law firm that serves public and private institutional investors, as well as retail investors, in seeking recoveries for investment losses.

Charles C. Foti, Jr.

The former Attorney General of Louisiana and a partner at KSF.

Lewis Kahn

The managing partner at KSF who is notifying Ultragenyx investors about the class action lawsuit.

Steven Bailey

The lead plaintiff in the class action lawsuit against Ultragenyx Pharmaceutical Inc.

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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 (Business Wire)

What’s next

The judge in the case will decide on whether to allow the class action lawsuit to proceed after the April 6, 2026 application deadline for lead plaintiff.

The takeaway

This lawsuit highlights the risks and potential consequences for pharmaceutical companies when their drug candidates fail to meet clinical trial endpoints. Investors who suffered losses due to Ultragenyx's alleged securities fraud will have an opportunity to seek recourse through the class action lawsuit.