Ultragenyx Pharmaceutical Inc. (RARE) Securities Class Action Lawsuit Update

Ultragenyx Pharmaceutical Inc. (RARE) Securities Class Action Lawsuit Update

• Case Name: Bailey v. Ultragenyx Pharmaceutical Inc. et al.
• Case No.: 3:26-cv-01097
• Jurisdiction: U.S. District Court, Northern District of California
• Filed on: February 4, 2026
• Class Period: August 3, 2023-December 26, 2025

Introduction

In early 2026, investors filed a federal securities class action alleging that Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) made materially false or misleading statements regarding its Phase III clinical trials for setrusumab. The company repeatedly highlighted bone mineral density data from earlier studies and expressed confidence in the Phase III program, until the ORBIT and COSMIC studies failed to achieve statistical significance and the company’s share price declined following those disclosures.

The lawsuit alleges that these assurances inflated Ultragenyx’s share price throughout the class period, leaving shareholders exposed when the truth emerged in a series of sharp corrective disclosures.

“Most RARE shareholders never file or join the class action, which means they miss out on potential recovery funds,” said Attorney Joseph Levi.

Backdrop and Business Context

Ultragenyx Pharmaceutical Inc. is a biopharmaceutical company focused on therapies for rare and ultra-rare genetic diseases. A central pillar of its pipeline during the relevant period was setrusumab (UX143), a therapy being developed to treat osteogenesis imperfecta, a brittle-bone disorder marked by frequent fractures and chronic disability.

The company advanced setrusumab into two Phase III trials, ORBIT and COSMIC, aimed at demonstrating a reduction in annualized fracture rates across pediatric and young adult populations. Investor confidence became closely tied to management’s repeated references to Phase II data and expressions of confidence that Phase III results would demonstrate a reduction in fracture rates.

Promises Made vs. Reality

According to the complaint, Ultragenyx executives consistently told investors that increases in bone mineral density observed in earlier studies would necessarily correlate with fewer fractures in Phase III patients. Executives publicly expressed “high confidence” that the magnitude of bone-density improvement was sufficient to reduce fracture rates, and discussed variability and statistical thresholds in describing the Phase III program.

The lawsuit alleges that these statements omitted critical risks, namely, that Phase II results lacked placebo controls and that improvements in fracture rates could have been driven by heightened monitoring, increased standard of care, or behavioral changes rather than the drug itself. Internally, plaintiffs allege, the linkage between bone density and fracture reduction was far less certain than management conveyed.

Timeline of Alleged Misconduct and Disclosures

Throughout 2023 and 2024, Ultragenyx made public statements expressing confidence in the ORBIT and COSMIC trials. The complaint alleges that these statements did not fully disclose the risks associated with patient variability and trial design. The narrative shifted on July 9, 2025, when Ultragenyx disclosed that the Phase III ORBIT study failed to achieve statistical significance at its second interim analysis. The company stated that the studies would continue toward final analysis, but the market reaction was immediate. Shares fell more than 25% in a single trading day.

The reckoning deepened on December 29, 2025, when Ultragenyx announced that neither the ORBIT nor COSMIC studies achieved statistical significance on their primary endpoints. The stock fell again, this time by more than 40%, erasing approximately a billion in market capitalization almost overnight.

Investor Harm and Market Reaction

The complaint ties these price declines directly to the alleged corrective disclosures. Investors who purchased RARE shares during the class period are alleged to have paid artificially inflated prices based on misrepresentations about trial prospects and risk controls.

Following the December 29, 2025 Phase III readouts, some analysts expressed increased caution about setrusumab’s prospects, noting that despite improvements in secondary endpoints such as bone mineral density, the failure to reduce annualized fracture rates raised questions about future regulatory and commercial opportunities. The lawsuit alleges that these reactions reflected the market’s belated realization that the drug’s clinical prospects had been overstated all along.

Litigation and Procedural Posture

The action is pending in the U.S. District Court for the Northern District of California. Plaintiffs assert claims under Sections 10(b) and 20(a) of the Securities Exchange Act and Rule 10b-5 against Ultragenyx and senior executives, including its CEO and Chief Medical Officer.

The complaint alleges scienter based on defendants’ access to internal trial data, repeated public assurances that contradicted emerging risks, and their control over corporate disclosures. The case is at an early procedural stage, with plaintiffs seeking to represent all investors who purchased Ultragenyx common stock during the defined class period.

Shareholder Sentiment

Investor reaction turned sharply negative after Ultragenyx disclosed in late December 2025 that the Phase III ORBIT and COSMIC trials for setrusumab failed to meet their primary endpoints. Retail discussion across platforms such as Reddit and Stocktwits focused heavily on the scale of the selloff and the implications for the company’s brittle-bone disease program. Many commenters pointed to the roughly 40%+ single-day drop in RARE shares following the announcement as evidence of how heavily the market had been weighting the program’s success. Reuters reported that Ultragenyx shares fell approximately 43.5% after the trial results were disclosed, triggering widespread discussion among retail investors about the failed primary endpoints and the gap between earlier optimism around bone-density improvements and the final fracture-rate results.

Analyst Commentary

Financial analysts across major firms swiftly re-evaluated Ultragenyx's valuation, citing "fractured" confidence in the company’s rare bone disease pipeline. According to The Motley Fool, several major institutions drastically lowered their outlooks on the news: Citigroup reduced price target from $103 to $50; Barclays slashed target from $81 to $50, citing "limited approval prospects" for the drug; and Cantor Fitzgerald adjusted its target from $105 down to $84.

Analysts at Scrip (Citeline) warned of an "uphill battle" for setrusumab, noting that while the drug hit secondary endpoints for bone density, the failure to reduce physical fractures makes a path to FDA approval highly unlikely. Per MorningStar’s MarketWatch, the focus of the investment community has shifted away from setrusumab and toward the company’s upcoming gene therapy data for Angelman syndrome, though analysts remain cautious given the recent loss of roughly $1.4 billion in market capitalization.

SEC Filings & Risk Factors

Ultragenyx’s public filings during the class period included general warnings about clinical trial risk and variability. The complaint alleges, however, that these risk factors were undermined by more specific and confident oral and written statements that minimized the likelihood of failure and overstated the predictive value of earlier data.

Plaintiffs argue that investors were not adequately informed that Phase II results lacked placebo controls or that fracture-rate reductions could stem from non-drug factors. These omissions, they allege, rendered the company’s risk disclosures incomplete and misleading.

Conclusion: Implications for Investors

The Ultragenyx securities class action focuses on whether the company’s public statements about setrusumab’s clinical prospects were materially misleading in light of later disclosures that the Phase III trials did not meet their primary endpoints. The complaint alleges that investors were not fully informed about risks relating to the interpretation of earlier data and the likelihood of achieving statistically significant fracture reductions.

Following the Phase III results, Ultragenyx’s share price declined sharply, reflecting the market’s reaction to the disclosed outcomes. The case will turn on whether the challenged statements and omissions are ultimately found to have violated federal securities laws.

How to Join the Ultragenyx Pharmaceutical Inc. (RARE) Class Action

• Confirm you purchased RARE shares during the relevant class period
• Review eligibility details
• Click here to check eligibility

Disclaimer: This shareholder alert is for informational purposes only and does not constitute legal advice. Consult a qualified attorney for personalized guidance. No specific outcomes are guaranteed.