NEW YORK, Feb. 23, 2026 (GLOBE NEWSWIRE) -- Levi & Korsinsky, LLP notifies investors in Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) that a class action lawsuit has been filed on behalf of shareholders who purchased securities between August 3, 2023 and December 26, 2025.
Click here to learn more about this case
You may also contact Joseph E. Levi, Esq. at jlevi@levikorsinsky.com or (212) 363-7500.
The Alleged Phase III Study Design Methodology
Rare disease drug development presents unique challenges in clinical trial design. For osteogenesis imperfecta ("OI"), a genetic bone disorder characterized by fragile bones, measuring treatment efficacy requires careful attention to patient selection, control group composition, and endpoint variability. The lawsuit alleges that management's repeated expressions of confidence in the Phase III Orbit and Cosmic studies' ability to demonstrate reduced annualized fracture rates ("AFR") were misleading given inherent study design limitations.
How Study Design Allegedly Affected Results
According to the lawsuit, the complaint raises serious questions about whether the Phase III studies were adequately powered and designed to demonstrate setrusumab's purported benefits. The lawsuit contends that management knew or should have known that basing Phase III assumptions on Phase II data without a placebo control group created substantial risk that observed fracture reductions could be attributable to factors other than drug efficacy.
Key Clinical Trial Design Allegations for Shareholders
• The complaint alleges Phase III study design relied heavily on uncontrolled Phase II observations that could not rule out placebo effects
• Increased enrollment of severe OI types (Type III and IV) in Phase III allegedly created patient population mismatches versus Phase II assumptions
• The lawsuit alleges management dismissed concerns about increased patient activity potentially confounding fracture rate measurements
• According to the complaint, the studies' negative binomial regression model assumptions may have been inappropriate for the actual fracture distribution observed
• The lawsuit contends management's confidence statements understated known variability risks inherent in rare disease fracture rate endpoints
The Bone Mineral Density Disconnect
The complaint alleges that while setrusumab achieved statistically significant improvements in bone mineral density ("BMD"), these improvements did not translate to the primary endpoint of reduced fracture rates. This disconnect between surrogate and clinical endpoints raises questions about the validity of management's repeated assertions that BMD improvements would "necessarily translate" to fracture reduction.
"This case presents important questions about clinical trial endpoint disclosure obligations in the rare disease pharmaceutical sector," said Joseph E. Levi, Esq., managing partner of Levi & Korsinsky, LLP. "We are committed to pursuing justice for investors who relied on the company's public statements about its Phase III study design and expected outcomes."
Get more information or contact Joseph E. Levi, Esq. at (212) 363-7500.
ABOUT LEVI & KORSINSKY, LLP
Over the past 20 years, Levi & Korsinsky has secured hundreds of millions of dollars for aggrieved shareholders. The firm has extensive expertise in complex securities litigation and a team of over 70 employees. For seven consecutive years, Levi & Korsinsky has ranked in ISS Securities Class Action Services' Top 50 Report. Applications to serve as lead plaintiff must be filed by April 6, 2026.
CONTACT:
Levi & Korsinsky, LLP
Joseph E. Levi, Esq.
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New York, NY 10004
(212) 363-7500
jlevi@levikorsinsky.com
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