Investor Notice: Shareholder Rights Law Firm Robbins LLP Informs Investors of the Ultragenyx Pharmaceutical Inc. Securities Class Action Lawsuit

SAN DIEGO--(BUSINESS WIRE)--Robbins LLP informs stockholders that a class action was filed on behalf of all investors who purchased or otherwise acquired Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) common stock between August 3, 2023 and December 26, 2025. Ultragenyx is a biopharmaceutical company focused on rare and ultrarare genetic disorders.

For more information, submit a form, email attorney Aaron Dumas, Jr., or give us a call at [phone].

The Allegations: Robbins LLP is Investigating Allegations that Ultragenyx Pharmaceutical Inc. (RARE) Misled Investors Regarding Phase III Orbit and Cosmic Studies for Setrusumab

According to the complaint, during the class period, defendants provided investors with material information concerning Ultragenyx’s expected results for its Phase III Orbit and Cosmic Studies, which tested setrusumab (UX 143) in patients with Osteogenesis Imperfecta (“OI”). Defendants’ statements included, among other things, confidence in setrusumab’s ability to ultimately trigger a decrease in the OI patients’ annualized fracture rate, alongside confidence in the study designs to demonstrate such ability and reduce testing variability that could interfere with such a result.

Plaintiff alleges that defendants provided these overwhelmingly positive statements to investors while, at the same time, disseminating materially false and misleading statements and/or concealing material adverse facts concerning the true state of setrusumab’s potential and the true risk inherent in the study protocols put forth; notably, that, while setrusumab does increase material bone density, this increase does not correlate to a decrease in annualized fracture rates or otherwise the Phase III Orbit and Cosmic studies were much less likely to be able to demonstrate such a link than management claimed. Such statements absent these material facts caused Plaintiff and other shareholders to purchase Ultragenyx’s securities at artificially inflated prices.

The complaint alleges that on December 29, 2025, Ultragenyx announced that both its Phase III Orbit and Cosmic Studies had not “achieved statistical significance against the primary endpoints of reduction in annualized clinical fracture rate compared to placebo or bisphosphonates, respectively.” The Company attributed the study failure to a “low fracture rate in the placebo group” of Orbit and a trend that fell shy of statistical significance in Cosmic. On this news, the price of Ultragenyx's stock fell from a closing market price of $34.19 per share on December 26, 2025, to $19.72 per share on December 29, 2025, a decline of about 42.32% in the span of just a single day.

What Now: You may be eligible to participate in the class action against Ultragenyx Pharmaceutical Inc. Shareholders who wish to serve as lead plaintiff for the class should contact Robbins LLP. The lead plaintiff is a representative party who acts on behalf of other class members in directing the litigation. You do not have to participate in the case to be eligible for a recovery. If you choose to take no action, you can remain an absent class member. For more information, click here.

All representation is on a contingency fee basis. Shareholders pay no fees or expenses.

About Robbins LLP: A recognized leader in shareholder rights litigation, the attorneys and staff of Robbins LLP have been dedicated to helping shareholders recover losses, improve corporate governance structures, and hold company executives accountable for their wrongdoing since 2002.

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