Ultragenyx Pharmaceutical(US:RARE) TMX Newsfile·2026-03-16 13:21Core Viewpoint - A class action lawsuit has been filed against Ultragenyx Pharmaceutical Inc. for allegedly misleading investors regarding the efficacy of its studies on setrusumab for Osteogenesis Imperfecta, leading to a significant drop in share price [1][3]. Company Overview - Ultragenyx Pharmaceutical Inc. is a biopharmaceutical company based in Novato, California, focusing on treatments for rare diseases [2]. Legal Action Details - The lawsuit is on behalf of investors who purchased Ultragenyx common stock from August 3, 2023, to December 26, 2025, with a deadline of April 6, 2026, for potential lead plaintiff representatives [1][2]. - The complaint alleges that Ultragenyx raised investor expectations about the ORBIT and COSMIC studies while concealing that these studies did not significantly reduce clinical fracture rates compared to control groups [3]. Financial Impact - Following the disclosure of the study results, Ultragenyx's share price fell from $34.19 on December 26, 2025, to $19.72 on December 29, 2025, representing a loss of over 42% in a single day [3].