Securities Suits Claim Ultragenyx Pharmaceutical Overstated Setrusumab Prospects After Phase III Failures

Lawsuits Accuse Ultragenyx of Overstating Setrusumab Prospects

Several national plaintiffs’ firms announce competing securities class actions against Ultragenyx Pharmaceutical, alleging the company misleads investors about the clinical prospects of setrusumab in Osteogenesis Imperfecta (OI). The complaints, filed on behalf of purchasers of Ultragenyx common stock during an August 3, 2023 to December 26, 2025 class period, assert the company’s public statements paint an overly positive picture of its ORBIT and COSMIC Phase III programmes. Firms bringing actions include Berger Montague, Rosen Law Firm, The Schall Law Firm and DJS Law Group, each saying potential class members must move for lead plaintiff appointment by April 6, 2026.

The lawsuits focus on accusations that Ultragenyx and certain executives misrepresented the relationship between bone mineral density (BMD) gains from setrusumab and clinical benefit in reducing fracture rates, and that the Phase III study protocols carried risks management downplayed. Plaintiffs point to Ultragenyx’s December 29, 2025 disclosure that neither ORBIT nor COSMIC meets its primary endpoint of reducing annualised clinical fracture rate as the corrective event. Complaints allege those prior statements artificially inflate market perceptions of setrusumab’s therapeutic potential and seek recovery under Sections 10(b) and 20(a) of the Securities Exchange Act and SEC Rule 10b‑5.

The filings emphasise typical securities-litigation remedies and procedural steps: appointment of a lead plaintiff, class certification and claims for damages. The announcing firms highlight their track records in securities and class-action recoveries and provide portals, phone lines and contingency-fee arrangements for affected shareholders. They urge eligible investors to act before the April 6 deadline to preserve rights and potentially influence litigation strategy, noting that failure to move could foreclose lead plaintiff opportunities.

Ultragenyx and setrusumab in context

Ultragenyx, based in Novato, California, is a biopharmaceutical company focused on treatments for rare genetic diseases. Setrusumab, an investigational monoclonal antibody developed for OI, has shown increases in BMD in earlier studies; the current litigation centres on whether those surrogate changes meaningfully translate into reduced fracture incidence in patients.

Broader biotech disclosure trend

The wave of filings reflects a broader pattern in biotech where late‑stage clinical failures trigger securities litigation alleging inadequate disclosure of clinical risks or overstated efficacy projections. Industry observers say such suits can prompt closer scrutiny of how companies communicate trial design, surrogate endpoints and the limitations of early efficacy signals to investors and clinicians.