Ultragenyx Pharmaceutical Inc. Class Action Lawsuit – RARE

According to the complaint, defendants provided overwhelmingly positive statements to investors while, at the same time, disseminating materially false and misleading statements and/or concealing material adverse facts concerning the true state of setrusumab’s potential and the true risk inherent in the study protocols put forth; notably, that, while setrusumab does increase material bone density, this increase does not correlate to a decrease in annualized fracture rates or otherwise the Phase III Orbit and Cosmic studies were much less likely to be able to demonstrate such a link than management claimed.

On December 29, 2025, Ultragenyx announced that both its Phase III Orbit and Cosmic Studies had not “achieved statistical significance against the primary endpoints of reduction in annualized clinical fracture rate compared to placebo or bisphosphonates, respectively.” The Company attributed the study failure to a “low fracture rate in the placebo group” of Orbit and a trend that fell shy of statistical significance in Cosmic.

Following this news, the price of Ultragenyx’s common stock declined dramatically. From a closing market price of $34.19 per share on December 26, 2025, Ultragenyx’s stock price fell to $19.72 per share on December 29, 2025, a decline of about 42.32% in the span of just a single day.