A class action lawsuit has been filed against Altimmune Inc., a clinical-stage biopharmaceutical company based in Gaithersburg, Maryland. The lawsuit is on behalf of investors who acquired publicly traded securities of Altimmune between August 10, 2023, and June 25, 2025. The litigation follows Altimmune's announcement on June 26, 2025, regarding the topline results from its IMPACT Phase 2b trial of Pemvidutide for treating metabolic dysfunction-associated steatohepatitis (MASH). The company reported a failure to achieve statistical significance in the fibrosis reduction primary endpoint, attributing it to a higher-than-expected placebo response. This announcement led to a significant 53.2% drop in Altimmune's stock price. Investors affected during the specified period have until October 6, 2025, to seek to be appointed as lead plaintiff representatives in the class action.