Lawsuit Alleges Ultragenyx Pharmaceutical Misled Investors About Setrusumab Phase III Failures

Allegations Focus on Setrusumab Trial Disclosures

Plaintiffs allege Ultragenyx Pharmaceutical misleads investors about the clinical prospects of setrusumab, its antibody candidate for osteogenesis imperfecta (OI). Complaints filed in the U.S. District Court for the Northern District of California assert that company statements repeatedly portray confidence that setrusumab will reduce annualized fracture rate (AFR) and that Phase III Orbit and Cosmic study designs will limit variability, while withholding information that would undercut those assurances. The litigation centers on whether Ultragenyx knew or should have known that its public representations lacked a reasonable evidentiary basis.

At the heart of the complaints is the company’s reliance on Phase II data that plaintiffs say lack a placebo control, which defendants allegedly failed to fully disclose as a limitation. Plaintiffs contend Ultragenyx benchmarked a second interim analysis for the Phase III Orbit study on the basis of those non‑controlled results, downplaying the risk that the study would not achieve the statistical significance required to perform a second interim analysis. The suits argue that apparent reductions in AFR reported in earlier testing could reflect improved standard of care or placebo effects rather than true treatment efficacy, making prior optimism and public statements misleading.

The litigation seeks lead plaintiffs to steer the class action and potential recovery for purchasers of Ultragenyx common stock during the class period. Multiple plaintiff firms — including Rosen Law, Kessler Topaz Meltzer & Check and Robbins Geller Rudman & Dowd — notify eligible investors and urge timely motions for lead‑plaintiff appointment by the April 6, 2026 deadline. The suits assert claims under securities laws alleging materially false or misleading statements and omissions relating to setrusumab and the conduct and interpretation of the Phase III trials.

Background on Trials and Disclosures

Ultragenyx discloses that the Phase III Orbit and Cosmic studies for setrusumab fail to meet primary endpoints for reduction in annualized clinical fracture rate relative to placebo; complaints reference a July 9, 2025 disclosure that a second interim analysis did not reach statistical significance and a December 29, 2025 announcement that both studies missed primary endpoints.

Procedural notices and contact details

The case is captioned Bailey v. Ultragenyx Pharmaceutical Inc., No. 26‑cv‑01097 (N.D. Cal.). Potential lead plaintiffs who purchased common stock between Aug. 3, 2023 and Dec. 26, 2025 are instructed by the notifying firms to move the court by April 6, 2026 and may contact the respective firms for information or representation.