Ultragenyx Pharmaceutical Faces Class Actions Over Setrusumab Phase III Efficacy Claims

Ultragenyx Faces Claims Over Setrusumab Trial Statements

Main development: Allegations on clinical claims weigh on Ultragenyx

Three national plaintiff firms file class actions accusing Ultragenyx Pharmaceutical Inc. of making false or misleading statements about the clinical prospects of setrusumab, the company’s investigational therapy for osteogenesis imperfecta (OI). The complaints, filed Feb. 9, 2026, assert that Ultragenyx overstated the likelihood that increases in bone mineral density (BMD) observed with setrusumab would translate into meaningful reductions in annualized fracture rates (AFR) in Phase III trials. The suits single out the ORBIT and COSMIC studies as being less likely than management portrayed to demonstrate a statistically significant link between BMD gains and reduced fractures.

The complaints centre on the Phase III ORBIT study, which the plaintiffs say failed to achieve a statistically significant reduction in AFR, a primary clinical endpoint for patients with OI. Plaintiffs allege company statements created an overly optimistic picture of the drug’s potential and the robustness of the trial protocols, while concealing material risks that made demonstration of reduced fracture rates unlikely. The filings argue that when trial results undermining those assertions reach the market, investors suffer economic loss; the cases assert violations of the anti-fraud provisions of the Securities Exchange Act.

While the suits seek to recover damages on behalf of purchasers during a defined class period, they also pose potential operational and governance implications for Ultragenyx beyond investor claims. The litigation places scrutiny on clinical trial design, corporate disclosures about surrogate endpoints such as BMD, and the company’s communications with physicians and regulators. The complaints remain at an early procedural stage; class certification and any determination on the merits are pending in federal court.

Lead-plaintiff deadline and class period

The complaints identify a class period from Aug. 3, 2023 through Dec. 26, 2025 and set an April 6, 2026 deadline for investors seeking to move for appointment as lead plaintiff. Firms involved are inviting affected shareholders to contact them to preserve potential claims; the notices state that participation does not require lead-plaintiff appointment and that absent action prospective plaintiffs may remain outside representation.

Plaintiffs’ counsel and asserted legal basis

Rosen Law Firm, The Schall Law Firm and DJS Law Group each issue notices describing alleged violations of Sections 10(b) and 20(a) of the Securities Exchange Act and SEC Rule 10b-5. Rosen highlights its prior securities recoveries and rankings in its outreach; the firms emphasize their experience in securities class actions and urge timely contact from purported class members.