Collier v. Altimmune, Inc. et al

NATURE OF THE ACTION

1. This is a federal securities class action on behalf of all investors who purchased or otherwise acquired Altimmune securities between August 10, 2023 and June 25, 2025 , inclusive (the “Class Period”), seeking to recover damages caused by Defendants’ violations of the federal securities laws (the “Class”).

2. The alleged misrepresentations in this case focus on Altimmune’s failure to achieve statistical significance in its analysis of the fibrosis reduction primary endpoint in its IMPACT Phase 2b MASH trial. In pertinent part, Defendants provided the public with overwhelmingly positive statements leading up to the announcement of topline results that failed to account for the fibrosis reduction observed in the placebo group.

3. Defendants provided these overwhelmingly positive statements to investors while, at the same time, misrepresenting and/or concealing material adverse facts concerning the true state of the results observed in Altimmune’s IMPACT Phase 2b MASH trial. Altimmune’s executives repeatedly touted their positive expectations and even went as far as to title the press release announcing IMPACT Phase 2b MASH trial topline results “Announces Positive Topline Results from the IMPACT Phase 2b MASH trial of Pemvidutide in the Treatment of MASH,” completely disregarding that one of two primary endpoints was not found to be statistically significant. In fact, Defendants spent minimal time discussing the aforementioned failure during the Special Call hosted by Altimmune pertaining to the topline results, rather stating that the Company hoped for better results in the Phase 3 trial.

4. On June 26, 2025 , Altimmune published a press release announcing topline results from the IMPACT Phase 2b MASH trial of Pemvidutide in the Treatment of MASH. While Defendants had continuously provided inflated expectations ahead of these results, the analysis

showed a pointed failure by the Company to achieve statistical significance in its analysis of the fibrosis reduction primary endpoint in its IMPACT Phase 2b MASH trial. In particular, while a positive trend in fibrosis improvement was observed, statistical significance was not met due to a higher-than-expected placebo response. When questioned about this concerning miss, Defendants answered indifferently, attributing this result to the Phase 2 nature of the trial and stated that Altimmune was hoping for better results following the Phase 3 trial.

5. Investors and analysts reacted immediately to Altimmune’s revelation. The price of Altimmune’s common stock declined dramatically. From a closing market price of $7.71 per share on June 25, 2025 , Altimmune’s stock price fell to $3.61 per share on June 26, 2025 , a decline of 53.2% in the span of just a single day. Investors who purchased Altimmune stock prior to this disclosure did so based on materially misleading information and suffered damages as a result.

JURISDICTION AND VENUE

6. Plaintiff brings this action, on behalf of himself and other similarly situated investors, to recover losses sustained in connection with Defendants’ fraud.

7. The claims asserted herein arise under and pursuant to §§10(b) and 20(a) of the Exchange Act (15 U.S.C. §§ 78j(b) and 78t(a)) and Rule 10b-5 promulgated thereunder by the SEC (17 C.F.R. §240.10b-5).

8. This Court has jurisdiction over the subject matter of this action pursuant to 28 U.S.C. §§ 1331 and 1337 , and Section 27 of the Exchange Act, 15 U.S.C. §78aa.

9. Venue is proper in this District pursuant to §27 of the Exchange Act and 28 U.S.C. § 1391 (b), as a significant portion of Defendant Altimmune’s business, actions, and the subsequent damages to Plaintiff and the Class, took place within this District.