Concurrent improvement across key non-invasive tests underscores convergence of

pemvidutide effects on MASH disease activity and fibrosis

AI-based digital pathology analyses further demonstrate antifibrotic effects of pemvidutide

at 24 weeks

GAITHERSBURG, Md., May 27, 2026 (GLOBE NEWSWIRE) -- Altimmune, Inc. (NASDAQ:ALT), a late clinical-stage biopharmaceutical company developing pemvidutide to address serious liver diseases, today announced that new analyses of data from the IMPACT Phase 2b trial demonstrated that treatment with pemvidutide, an investigational, balanced 1:1 glucagon/GLP-1 dual receptor agonist, is associated with concurrent improvements across multiple non-invasive tests (NITs) of metabolic dysfunction-associated steatohepatitis (MASH) activity and fibrosis. These new data reinforce a consistent and clinically meaningful treatment effect observed at just 24 weeks. These findings are based on analyses of overlapping markers of liver fat, inflammation and fibrosis. The analyses are further supported by separate AI-based digital pathology data showing significant improvements in fibrosis stage by HistoIndex qFibrosis® at 24 weeks, providing potent evidence of the antifibrotic potential of pemvidutide.

The data are being presented today and Friday in poster sessions, including a late-breaking poster presentation, at the European Association for the Study of the Liver (EASL) Congress 2026 in Barcelona, Spain.

"The ability of pemvidutide to demonstrate concurrent improvements across multiple non-invasive markers – and to see those findings supported by histologic measures of fibrosis – provides a more comprehensive and clinically meaningful view of its potential beneficial effect in patients with MASH," said Naim Alkhouri, MD, Chief Medical Officer, Summit Clinical Research. "These results point to the potential ability of pemvidutide to address multiple dimensions of disease biology, including fibrosis, and support its potential to target key drivers of MASH."

Highlights of the data presented at EASL 2026 include:

Pemvidutide treatment resulted in significant increases in the percentage of patients achieving concurrent improvements across key NITs compared with placebo at 24 weeks – including in liver fat content (LFC), alanine aminotransferase (ALT), liver stiffness measurement (LSM) and enhanced liver fibrosis (ELF).
37.8% of patients taking pemvidutide 1.2 mg and 22.7% of patients taking pemvidutide 1.8 mg achieved concurrent >0.5 ELF reduction plus >30% LSM reduction compared with 8.3% of patients taking placebo (p=0.0002 and p=0.02, respectively).

These overlapping NIT responses provide a more stringent and clinically meaningful assessment of treatment effect and also evidence of improvement across multiple dimensions of disease biology. The findings are further supported by AI-based digital pathology analyses using qFibrosis, which utilizes advanced Second Harmonic Generation (SHG)/Two-Photon Excitation Fluorescence (TPEF) imaging to quantify fibrosis across the entire biopsy sample, enabling detection of continuous and intra-stage changes in fibrosis. Those results showed:

Pemvidutide treatment led to significant reductions in continuous fibrosis values versus placebo.
68.6% of patients taking pemvidutide 1.2 mg and 54.5% of patients taking pemvidutide 1.8 mg achieved ≥1 stage qFibrosis regression compared with 29.6% of patients taking placebo (p<0.001 and p=0.002, respectively) after 24 weeks of treatment.

"The consistency of these findings across non-invasive markers and advanced imaging approaches reflects the potential early impact of pemvidutide in addressing MASH," said Christophe Arbet-Engels, M.D., Ph.D., Chief Medical Officer of Altimmune. "These multiple consistent analyses strengthen our confidence in pemvidutide and its potential to address significant unmet needs among patients living with MASH. In addition, 48-week data demonstrating a clear dose effect at the 1.8 mg dose further reinforces our confidence in the robustness and durability of the clinical response. Based on these promising Phase 2b clinical data, we are excited to begin patient enrollment in our PERFORMA Phase 3 trial of pemvidutide in patients with MASH in the second half of this year."

About the IMPACT Phase 2b Study

The randomized, placebo-controlled, double-blind IMPACT Phase 2b trial (NCT05989711) enrolled 212 participants with biopsy-confirmed metabolic dysfunction-associated steatohepatitis (MASH) and fibrosis stages F2 or F3, with and without diabetes. Study participants were randomized 1:2:2 to receive weekly subcutaneous pemvidutide doses at either 1.2 mg, 1.8 mg or placebo for 48 weeks. The primary efficacy endpoints, measured at 24 weeks, were MASH resolution without worsening of fibrosis, or fibrosis improvement without worsening of MASH. Secondary endpoints included non-invasive tests of fibrosis and weight loss measured at 24 and 48 weeks.

About Pemvidutide

Pemvidutide is a novel, investigational peptide with balanced 1:1 glucagon/GLP-1 dual receptor agonist activity, in development for the treatment of metabolic dysfunction-associated steatohepatitis (MASH), alcohol use disorder (AUD) and alcohol-associated liver disease (ALD). The activation of glucagon receptors results in direct effects on the liver, including reductions in liver fat, inflammation and fibrosis, while GLP-1 receptors mediate metabolic effects such as appetite suppression and weight loss.

The FDA granted Fast Track designations to pemvidutide for the treatment of MASH and AUD, as well as Breakthrough Therapy Designation for MASH. In December 2025, the Company announced 48-week data from the IMPACT Phase 2b trial in MASH. The RECLAIM Phase 2 trial in AUD completed enrollment in November 2025 and topline data are expected in third quarter 2026. The RESTORE trial in ALD was initiated in July 2025, and enrollment completion is expected in the third quarter 2026. The Company plans to initiate the PERFORMA Phase 3 trial, a multinational, randomized, double-blind, placebo-controlled, parallel-group study of pemvidutide in patients with MASH in the second half of 2026.

About Altimmune

Altimmune is a late clinical-stage biopharmaceutical company developing therapies for patients with serious liver diseases. The Company's lead candidate, pemvidutide, is a unique dual-action investigational therapy targeting both glucagon and GLP-1 receptors in a balanced 1:1 ratio in development for the treatment of metabolic dysfunction-associated steatohepatitis (MASH), alcohol use disorder (AUD) and alcohol-associated liver disease (ALD). For more information, please visit www.altimmune.com.

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Forward-Looking Statements

Any statements made in this press release related to the development or commercialization of pemvidutide, an investigational product candidate, and other business, regulatory and financial matters including without limitation, clinical trial study design, status, correspondence, results and data, including the ongoing RECLAIM and RESTORE trials and planned PERFORMA Phase 3 trial, the timing of key milestones for the Company's clinical programs, including the anticipated launch of the PERFORMA Phase 3 trial in MASH, future plans or expectations for pemvidutide for the treatment of MASH, AUD and ALD, the potential benefits of Fast Track and Breakthrough Therapy Designations, including potential regulatory timeline and approval benefits, the Company's financial position, and the prospects for receiving regulatory approval or commercializing or selling any product or drug candidates, financial results, and the impact of the changes to our leadership and governance structure, are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. In addition, when or if used in this press release, the words "may," "could," "should," "anticipate," "believe," "estimate," "expect," "intend," "plan," "predict" and similar expressions and their variants, as they relate to Altimmune, Inc. may identify forward-looking statements. The Company cautions that these forward-looking statements are subject to numerous assumptions, risks, and uncertainties, which change over time. Important factors that may cause actual results to differ materially from the results discussed in the forward-looking statements or historical experience include risks and uncertainties, including risks relating to: delays in regulatory review, manufacturing and supply chain interruptions, access to clinical sites, enrollment, adverse effects on healthcare systems and disruption of the global economy; the reliability of the results of studies relating to human safety and possible adverse effects resulting from the administration of the Company's product candidates; the Company's ability to manufacture clinical trial materials on the timelines anticipated; and the success of future product advancements, including the success of future clinical trials. Further information on the factors and risks that could affect the Company's business, financial conditions and results of operations are contained in the Company's filings with the U.S. Securities and Exchange Commission, including under the heading "Risk Factors" in the Company's most recent annual report on Form 10-K, quarterly report on Form 10-Q and the Company's other filings with the SEC, which are available at www.sec.gov.

Investor Contact:

Luis Sanay, CFA

Vice President, Investor Relations

ir@altimmune.com

Media Contact:

Real Chemistry

altimmune@realchemistry.com

New IMPACT Phase 2b Data Highlight Concurrent Improvements Across Multiple Non-Invasive Markers and qFibrosis-Measured Fibrosis Regression with Pemvidutide in MASH at EASL 2026