A class action lawsuit was filed against Altimmune (ALT) by Levi & Korsinsky on August 5, 2025. The plaintiffs (shareholders) alleged that they bought ALT stock at artificially inflated prices between August 10, 2023, and June 25, 2025 (Class Period) and are now seeking compensation for their financial losses. Investors who bought Altimmune stock during that period can click here to learn about joining the lawsuit.
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Altimmune is a late-stage biopharmaceutical company engaged in the discovery and development of peptide-based therapies for the treatment of obesity and metabolic dysfunction-associated steatohepatitis (MASH). Its lead candidate, pemvidutide, is a GLP-1/glucagon dual receptor agonist that helps reduce blood sugar levels and promotes weight loss.
Altimmune’s claims about the results observed in its IMPACT Phase 2b MASH trial involving pemvidutide are at the heart of the complaint.
Altimmune’s Misleading Claims
According to the lawsuit, Altimmune and two of its senior officers (the Defendants) repeatedly made false and misleading public statements throughout the Class Period. In particular, they are accused of omitting truthful information about the IMPACT Phase 2b MASH trial from SEC filings and related material.
During the Class Period, the CEO expressed enthusiasm about the compelling Phase 1b data in subjects with nonalcoholic fatty liver disease (NAFLD). The results demonstrated class-leading reductions in liver fat and markers of liver inflammation, supporting the potential to achieve robust rates of NASH resolution and fibrosis improvement in the ongoing IMPACT trial.
Additionally, in a business update dated November 7, 2023, Altimmune announced key details regarding its IMPACT Phase 2b NASH trial, stating that the primary endpoints are NASH resolution and fibrosis improvement after 24 weeks of treatment, with subjects followed for an additional 24 weeks to assess safety and further biomarker responses.
Finally, in an August 8, 2024, business update about its IMPACT Phase 2b NASH trial, the CEO stated that new data presented at the European Association for the Study of the Liver (EASL) meeting showed how pemvidutide can change the course of MASH disease. This strengthens the company’s confidence that the drug will succeed in improving MASH and reducing liver scarring in the trial.
However, subsequent events (detailed below) revealed that the defendants overstated expectations ahead of the IMPACT Phase 2b NASH trial results and failed to meet them.
Plaintiffs’ Arguments
The plaintiffs maintain that the defendants deceived investors by lying and withholding critical information about the company’s business and prospects during the Class Period. Importantly, the defendants failed to inform investors that although a positive trend in fibrosis improvement was observed, statistical significance was not achieved due to a higher-than-expected placebo response.
The information became clear on June 26, 2025, when Altimmune issued a press release announcing topline results from the IMPACT Phase 2b trial of Pemvidutide in the treatment of MASH and held a special call to discuss the matter.
During the call, the company’s Chief Medical Officer highlighted that the data demonstrated the treatment’s effect on improving liver fibrosis, based on pathologist reviews using the ITT method. Although there were positive signs of fibrosis improvement, the results did not reach statistical significance.
On the same call, he noted that when comparing these fibrosis improvement rates to other studies, pemvidutide at the 1.8 mg dose demonstrated a 34.5% absolute improvement, comparable to other drug candidates. However, achieving statistical significance was difficult because the placebo group exhibited a higher-than-expected response. Following the news, ALT stock collapsed 53.2% on the same day.
To conclude, the defendants failed to inform investors of the potential shortcomings of the IMPACT Phase 2b trial of Pemvidutide. Instead, the company merely stated that it was hoping for better results in the Phase 3 trial. Due to these issues, ALT stock has lost 47.4% so far this year.
