Altimmune, Inc. Securities Lawsuit Investigation

Shamis & Gentile P.A., a law firm that advocates for investors who are victims of securities fraud, is investigating potential claims against Altimmune, Inc. (ALT).

If you purchased or held Altimmune securities and suffered losses, you may be eligible to join this securities investigation and seek compensation.

About Altimmune

Altimmune is a clinical-stage biopharmaceutical company focused on developing innovative therapies for metabolic diseases and liver conditions. The company’s primary asset is pemvidutide, a drug candidate aimed at treating metabolic dysfunction-associated steatohepatitis (MASH) and obesity.

The Allegations

Altimmune is under investigation for allegedly making misleading statements and omissions regarding the clinical development of its lead drug candidate, pemvidutide. The focus is on statements made during the period from Dec. 1, 2023 through June 25, 2025, about the drug’s efficacy in its Phase 2b MASH trial.

On June 26, 2025, Altimmune publicly released topline 24-week data from the Phase 2b MASH trial. The company’s press release stated that the trial “met its primary endpoint” for MASH resolution, with results showing 59.1% and 52.1% achievement versus 19.1% for placebo. However, the same announcement revealed that the key fibrosis improvement endpoint showed only 31.8% and 34.5% versus 25.9% for placebo, with differences “not statistically significant”. This crucial detail, which was not highlighted in the headline, seemingly contradicted previous optimistic statements and led to a sharp market reaction.

Following this disclosure, Altimmune’s stock price plunged approximately 52% in a single day, dropping from about $11 per share to roughly $5.40 per share. This one-day collapse erased nearly half of the company’s market value, resulting in hundreds of millions of dollars in shareholder losses.

During the class period, Altimmune executives made several statements that may have misled investors. On Feb. 27, 2025, CEO Vipin K. Garg stated: “we are confident that pemvidutide will achieve statistically significant improvements in biopsy endpoints, both MASH resolution and fibrosis improvement, at trial readout”.

Similarly, on May 13, 2025, Garg said: “we believe that achieving statistical significance on MASH resolution and fibrosis improvement… would position pemvidutide as [a] best-in-class… therapy”. In both instances, an investor could have interpreted the company expressing confidence in achieving significance on both endpoints, yet the eventual results showed that fibrosis improvement did not reach statistical significance.

The June 26, 2025 press release described the results as “positive topline results” and called pemvidutide the “First product candidate to demonstrate significant MASH effects and weight loss at 24 weeks”. While technically accurate regarding MASH resolution, this characterization may have misled investors about the overall success of the trial by downplaying the lack of significance in fibrosis improvement.

Throughout the proposed class period, Altimmune promoted pemvidutide’s potential, with management describing its liver-fat reduction as “class-leading” and suggesting it could lead to “unprecedented reductions of fibrosis and measures of NASH”.

The investigation is examining whether Altimmune’s executives, who had significant financial incentives tied to the company’s valuation, knowingly or recklessly omitted material information about the trial’s likelihood of success on both endpoints. The company’s public statements and the subsequent revelation of the trial results have raised concerns about the adequacy and accuracy of disclosures to investors.

Your Rights and Next Steps

This is an active investigation into potential securities law violations by Altimmune. No lawsuit has been filed at this time, but the investigation may lead to a class action on behalf of investors who purchased Altimmune securities during the period from Dec. 1, 2023 through June 25, 2025.

Investors who purchased Altimmune stock and suffered financial losses after the June 26, 2025 corrective disclosure may be eligible to participate in any future class action. Lawyers are ready to help investors understand their rights, assess their losses, and determine whether they qualify to be part of the potential class.

If you believe you were affected, it is important to gather records of your Altimmune stock purchases and sales during the class period. Participation in a securities class action is typically free for investors, and there is no obligation to pursue a claim by submitting your information for review.

You May Be Entitled to Compensation

Securities investigations are time-sensitive. If you purchased Altimmune securities between Dec. 1, 2023 and June 25, 2025 and suffered losses, you may be eligible to join the investigation and seek compensation for your damages.

To protect your rights and learn more about your options, complete the form below to join the investigation.