Altimmune Announces that Pemvidutide Achieved Key Measures of Success at 48 Weeks in IMPACT Phase 2b MASH Trial

Rhea-AI Summary

Altimmune (Nasdaq: ALT) reported positive 48-week topline results from the IMPACT Phase 2b trial of pemvidutide in MASH patients on Dec 19, 2025. Both 1.2 mg and 1.8 mg doses produced statistically significant improvements in noninvasive fibrosis markers versus placebo, including ELF (‑0.49 and ‑0.58 vs +0.16; p<0.0001) and LSM (‑3.04 and ‑3.97 vs ‑0.03; p<0.05/0.001).

Additional 48-week highlights: liver fat down 45.2% and 54.7% (vs 8.2% placebo), ALT reductions ~‑38 IU/L (vs ‑10.3), weight loss 4.5% and 7.5% (vs 0.2%), low discontinuations, and FDA End‑of‑Phase 2 alignment to advance to a registrational Phase 3 planned for 2026.

Positive

• ELF reduced by 0.49 and 0.58 (1.2 mg/1.8 mg)
• LSM reduced by 3.04 and 3.97 kPa (1.2 mg/1.8 mg)
• Liver fat decreased 45.2% and 54.7% (1.2 mg/1.8 mg)
• Weight loss of 4.5% and 7.5% (1.2 mg/1.8 mg)
• Low treatment discontinuation: 0% and 1.2% (1.2 mg/1.8 mg)
• FDA End‑of‑Phase 2 alignment to registrational Phase 3 in 2026

Negative

• None.

News Market Reaction

-22.77% 3.0x vol

71 alerts

-22.77% News Effect

+8.9% Peak Tracked

-28.9% Trough Tracked

-$155M Valuation Impact

$526M Market Cap

3.0x Rel. Volume

On the day this news was published, ALT declined 22.77%, reflecting a significant negative market reaction. Argus tracked a peak move of +8.9% during that session. Argus tracked a trough of -28.9% from its starting point during tracking. Our momentum scanner triggered 71 alerts that day, indicating high trading interest and price volatility. This price movement removed approximately $155M from the company's valuation, bringing the market cap to $526M at that time. Trading volume was elevated at 3.0x the daily average, suggesting increased selling activity.

Data tracked by StockTitan Argus on the day of publication.

Key Figures

ELF reduction 1.2 mg: -0.49 vs +0.16 placebo ELF reduction 1.8 mg: -0.58 vs +0.16 placebo LSM reduction 1.8 mg: -3.97 vs -0.03 placebo +5 more

8 metrics

ELF reduction 1.2 mg -0.49 vs +0.16 placebo Mean change from baseline at 48 weeks (p<0.0001)

ELF reduction 1.8 mg -0.58 vs +0.16 placebo Mean change from baseline at 48 weeks (p<0.0001)

LSM reduction 1.8 mg -3.97 vs -0.03 placebo Mean change from baseline at 48 weeks (p<0.001)

Dual ELF+LSM responders 27.8% & 32.4% vs 3.2% placebo ≥0.5 ELF and 30% LSM reduction at 48 weeks

Liver fat reduction 45.2% & 54.7% vs 8.2% placebo Mean change from baseline at 48 weeks (both doses)

Weight loss 1.8 mg 7.5% vs 0.2% placebo Body weight change at 48 weeks, no plateau

ALT reduction -37.8 & -37.4 vs -10.3 IU/L Mean ALT change at 48 weeks (p<0.0001)

Discontinuations AEs 0% & 1.2% vs 3.5% placebo Adverse event–related treatment discontinuations

Market Reality Check

Price: $4.50 Vol: Volume 2,810,556 is below...

normal vol

$4.50 Last Close

Volume Volume 2,810,556 is below the 20-day average of 3,582,559 ahead of the data release. normal

Technical Price $5.05 was trading above the 200-day MA at $4.66 before this topline update.

Peers on Argus

Biotech peers showed mixed, mostly modest moves (e.g., TECX +1.16%, ALDX −4.93%)...

Biotech peers showed mixed, mostly modest moves (e.g., TECX +1.16%, ALDX −4.93%), suggesting this pemvidutide update is company-specific rather than part of a broad sector move.

Historical Context

5 past events · Latest: Dec 01 (Neutral)

Pattern 5 events

Date	Event	Sentiment	Move	Catalyst
Dec 01	CEO succession	Neutral	-6.3%	Announced leadership transition with CEO succession and timeline details.
Nov 26	Conference participation	Neutral	+0.6%	Planned fireside chat at healthcare conference with webcast access.
Nov 11	Clinical data publication	Positive	+0.5%	Lancet publication and major liver meeting presentation of 24-week IMPACT data.
Nov 07	AI fibrosis analysis	Positive	+4.3%	AI-based digital pathology showed significant fibrosis reduction vs placebo.
Nov 06	Earnings and pipeline	Positive	+5.1%	Q3 results, strengthened liquidity, and upcoming MASH regulatory milestones.

Pattern Detected

Recent pemvidutide and pipeline updates have generally seen positive or modestly positive price alignment, while corporate leadership news drew a sharper negative reaction.

Recent Company History

Over the last few months, Altimmune highlighted steady progress for pemvidutide. Q3 2025 updates on Nov 6 detailed a stronger cash position and upcoming IMPACT 48-week data. Subsequent AI-based fibrosis analyses and 24-week IMPACT results in November showed significant antifibrotic and metabolic effects, with mostly positive price follow-through. A CEO succession plan on Dec 1 drew a negative reaction. Today’s 48-week IMPACT topline extends that clinical narrative with longer-term NIT, weight-loss and safety data.

Regulatory & Risk Context

Active S-3 Shelf · $400,000,000

Shelf Active

Active S-3 Shelf Registration 2025-11-13

$400,000,000 registered capacity

An amended Form S-3/A filed on Nov 13, 2025 registers up to $400,000,000 of mixed securities. The shelf was not yet effective and had 0 recorded usages in the provided data, but, once effective, would allow Altimmune to raise capital for general corporate and clinical purposes via future offerings.

Market Pulse Summary

The stock dropped -22.8% in the session following this news. A negative reaction despite encouraging...

Analysis

The stock dropped -22.8% in the session following this news. A negative reaction despite encouraging 48-week antifibrotic and metabolic data would contrast with earlier positive alignment around pemvidutide updates, including the 4.31% rise on AI fibrosis analysis. Pressure could reflect concerns about future financing under the $400,000,000 shelf or the costs of Phase 3. Past divergence on leadership news shows the stock can move counter to fundamentals, so sentiment and capital-raising expectations may drive downside.

Key Terms

non-invasive tests, Enhanced Liver Fibrosis (ELF), Liver Stiffness Measurement (LSM), alanine aminotransferase (ALT), +4 more

8 terms

non-invasive tests medical

"statistically significant improvements across treatment arms in key non-invasive tests (NITs)"

Non-invasive tests are medical checks that gather diagnostic information without cutting into the body or inserting instruments into internal cavities, using methods like external imaging, breath or saliva sampling, and surface sensors. For investors, they matter because they tend to be lower-risk, quicker to adopt, cheaper to administer, and more acceptable to patients than surgical procedures, which can mean larger markets, faster revenue growth, and simpler regulatory paths.

Enhanced Liver Fibrosis (ELF) medical

"including Enhanced Liver Fibrosis (ELF) and Liver Stiffness Measurement (LSM), versus placebo"

A blood test that measures specific markers associated with liver scarring to estimate the amount and progression of fibrosis without needing a biopsy. Like a car inspection that looks for wear rather than opening the engine, it gives doctors and drug developers a noninvasive way to track liver damage, which matters to investors because results can influence the market for diagnostics, the value of treatments in development, and regulatory or clinical trial decisions.

Liver Stiffness Measurement (LSM) medical

"Enhanced Liver Fibrosis (ELF) and Liver Stiffness Measurement (LSM), versus placebo"

Liver stiffness measurement (LSM) is a noninvasive test that uses gentle mechanical waves to estimate how firm the liver is, similar to checking the ripeness of a fruit by how it springs back. Higher stiffness usually means more scarring or advanced liver disease, which affects patient treatment and prognosis. Investors care because LSM results drive demand for drugs, diagnostics and medical devices, influence clinical trial outcomes, and can alter forecasts for healthcare revenue and regulatory risk.

alanine aminotransferase (ALT) medical

"including liver fat content, alanine aminotransferase (ALT) and corrected T1 (cT1)"

Alanine aminotransferase (ALT) is a liver enzyme measured in blood that acts like a “check engine” light for the liver: higher levels usually indicate liver cell stress or damage. For investors, ALT matters because abnormal results can affect drug approvals, trigger additional safety testing, lead to regulatory scrutiny or liabilities for healthcare companies, and influence clinical trial outcomes and pharmaceutical valuations.

corrected T1 (cT1) medical

"alanine aminotransferase (ALT) and corrected T1 (cT1)"

Corrected T1 (cT1) is an MRI-based measurement that quantifies changes in liver tissue linked to inflammation and scarring, with adjustments made to remove distortions from iron and other factors so the reading reflects true tissue health. Investors care because cT1 serves as a noninvasive biomarker used in diagnostics and clinical trials to track disease progression or treatment response, influencing the commercial value of imaging tools, drugs, and diagnostic services — like using a cleaned lens to see the real condition of an asset.

dual receptor agonist medical

"pemvidutide, a balanced 1:1 glucagon/GLP-1 dual receptor agonist, in patients"

A dual receptor agonist is a drug that activates two different cell-surface receptors—proteins that trigger specific biological responses—so it delivers two therapeutic actions in one medicine, like a single key that turns two different locks. Investors care because such drugs can improve effectiveness or convenience compared with separate treatments, potentially boosting market appeal and pricing, but they also carry added development and regulatory risk that can affect clinical success and future revenue.

End-of-Phase 2 meeting regulatory

"End-of-Phase 2 meeting with FDA supports advancing to registrational Phase 3 trial"

An end-of-phase 2 meeting is a formal discussion between a drug developer and a regulatory agency to review mid-stage clinical results and agree on the plan and requirements for the larger, final tests needed for approval. It matters to investors because the meeting can clarify what evidence regulators will require, shape the cost and timeline for the next phase, and reduce uncertainty about whether a drug can advance toward market — like a checkpoint that determines whether a project gets the green light to move to the next, expensive stage.

Phase 3 trial medical

"supports advancing to registrational Phase 3 trial in MASH patients"

A Phase 3 trial is a large, late-stage test of a new drug or medical treatment done on many people to make sure it really works and is safe. For investors, it matters because a successful Phase 3 usually means the company can ask regulators to sell the product and could earn lots of money, while failure can sharply reduce the company’s value.

AI-generated analysis. Not financial advice.

Improvements observed in key non-invasive markers of fibrosis across treatment arms versus placebo, with continued reductions from 24-week timepoint

Additional weight loss from 24 to 48 weeks with 1.8 mg dose, without plateauing

Favorable tolerability profile of pemvidutide preserved at 48 weeks, reinforced by low treatment-related discontinuation rate

End-of-Phase 2 meeting with FDA supports advancing to registrational Phase 3 trial in MASH patients with moderate to advanced liver fibrosis

Conference call to be held today at 8:00 a.m. ET

GAITHERSBURG, Md., Dec. 19, 2025 (GLOBE NEWSWIRE) -- Altimmune, Inc. (Nasdaq: ALT), a late clinical-stage biopharmaceutical company developing therapies that address serious liver diseases, today announced positive topline results from the IMPACT Phase 2b trial of pemvidutide, a balanced 1:1 glucagon/GLP-1 dual receptor agonist, in patients with metabolic dysfunction-associated steatohepatitis (MASH) at 48 weeks.

Topline 48-week data from the IMPACT trial showed that treatment with pemvidutide achieved statistically significant improvements across treatment arms in key non-invasive tests (NITs), including Enhanced Liver Fibrosis (ELF) and Liver Stiffness Measurement (LSM), versus placebo. Importantly, these data exhibited continued reductions from week 24 and provide evidence of continued improvement in antifibrotic activity with both treatment doses. These are well-established markers of fibrosis and hepatic inflammation and are strongly associated with histological changes and liver related events. Additional weight loss was observed with the 1.8 mg dose compared to the IMPACT 24-week data, with no evidence of plateauing. The 48-week data also maintained the favorable tolerability profile seen at 24 weeks, including a lower discontinuation rate due to adverse events than placebo.

“The magnitude of response versus placebo on measures such as ELF and LSM at 48 weeks makes these data particularly compelling, as these noninvasive markers have been shown to correlate with histologic fibrosis stage. These results reinforce that pemvidutide may address both liver-specific and metabolic drivers of MASH without compromising tolerability – three critical elements of a potential effective treatment for this patient population,” said Mazen Noureddin, M.D., IMPACT trial principal investigator, Professor of Medicine at Houston Methodist Hospital and Co-Chairman of the Board for Summit and Pinnacle Clinical Research. “I am encouraged by the dose response observed and the performance of the 1.8 mg arm and I am eager to see this differentiated therapeutic candidate advance into Phase 3 evaluation.”

Highlights from the 48-Week Topline Results

• Pemvidutide-treated participants achieved statistically significant reductions in primary non-invasive markers of fibrosis, including Enhanced Liver Fibrosis (ELF) and Liver Stiffness Measurement (LSM).
  • ELF: 1.2 mg and 1.8 mg doses achieved a mean reduction from baseline of -0.49 and -0.58 respectively, vs. +0.16 in placebo-treated patients (p<0.0001, both doses).
  • LSM: 1.2 mg and 1.8 mg doses achieved a mean reduction from baseline of -3.04 (p<0.05) and -3.97 (p<0.001), respectively, vs. -0.03 in placebo-treated participants.
  • The proportion of participants receiving pemvidutide 1.2 mg and 1.8 mg that achieved both a ≥0.5 reduction in ELF and a 30% reduction in LSM were 27.8% (p<0.001) and 32.4% (p<0.0001) respectively, vs. 3.2% in placebo-treated participants.
• Pemvidutide-treated participants also achieved statistically significant reductions in key non-invasive measures of liver health and hepatic inflammation, including liver fat content, alanine aminotransferase (ALT) and corrected T1 (cT1).
  • Liver fat content: 1.2 mg and 1.8 mg doses achieved a mean reduction from baseline of 45.2% and 54.7% respectively, compared to 8.2% in participants who received placebo (p<0.0001).
  • ALT: 1.2 mg and 1.8 mg achieved a mean reduction from baseline of -37.8 IU/L and -37.4 IU/L respectively, vs. -10.3 IU/L in placebo-treated participants (p<0.0001, both doses).
  • cT1: 1.2 mg and 1.8 mg achieved a mean reduction from baseline of -124 and -140 milliseconds (ms) respectively, vs. -21 ms in placebo-treated participants (p<0.0001, both doses).
• Participants receiving pemvidutide 1.2 mg and 1.8 mg achieved weight loss of 4.5% and 7.5%, respectively, vs. 0.2% of placebo-treated participants (p<0.0001, both doses), with no plateauing at 48 weeks with the 1.8 mg dose.
• Adverse events leading to treatment discontinuation occurred in 0% and 1.2% of patients treated with pemvidutide 1.2 mg and 1.8 mg, respectively, vs. 3.5% of participants on placebo.
• No serious or severe AEs related to treatment were reported.
  
  

Additionally, the Company announced that it held a productive End-of-Phase 2 meeting with the U.S. Food and Drug Administration (FDA) which resulted in alignment on the parameters for a registrational Phase 3 trial of pemvidutide for MASH patients with moderate to advanced liver fibrosis. With the FDA’s recent qualification of AIM-MASH AI Assist, the Agency was open to the Company’s intent to integrate use of this AI tool into the Phase 3 trial. AIM-MASH AI Assist is intended to help standardize histologic assessment and reduce the time and resources needed for MASH drug development.

“With the benefit of FDA feedback and these 48-week data now in hand, we are greatly looking forward to progressing pemvidutide to a Phase 3 program which we intend to initiate in 2026. Strong evidence of antifibrotic improvements based upon non-invasive tests, combined with an attractive tolerability profile, highlight pemvidutide’s differentiation and potential to be a meaningful treatment option for the MASH patient community,” said Vipin Garg, Ph.D., Chief Executive Officer of Altimmune.

Conference Call and Webcast
Altimmune will host a conference call and webcast on Friday, December 19, 2025 at 8:00 am ET to review the IMPACT Phase 2b topline 48-week data. The conference call will be webcast live on Altimmune’s Investor Relations website. Participants who would like to join by phone may register here to receive the dial-in numbers and unique PIN to access the call. Following the conclusion of the call, the webcast will be available for replay on Altimmune’s Investor Relations website.

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 MASH
Metabolic dysfunction-associated steatohepatitis (MASH) is a progressive liver disease marked by fat accumulation, inflammation, and fibrosis in the liver. Without treatment, it can progress to cirrhosis, liver failure, or liver cancer, and is one of the most common reasons for liver transplantation in the U.S. Management relies largely on lifestyle changes, and currently approved treatment options may not fully address both the metabolic drivers and fibrosis that can pose long-term risk.

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, both areas of significant unmet medical need. In December 2025, the Company announced 48-week data from the IMPACT Phase 2b trial in MASH. Phase 2 trials in AUD (RECLAIM) and ALD (RESTORE) were initiated in May 2025 and July 2025, respectively, and are currently ongoing.

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 therapy targeting both glucagon and GLP-1 receptors in a balanced 1:1 ratio 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.

Forward-Looking Statement
Any statements made in this press release related to the clinical trial results, development or commercialization of pemvidutide, an investigational product candidate, and other business, regulatory and financial matters including without limitation, trial results and data, including the data and results from the 48-week IMPACT trial, and statements related to ELF, LSM, ALT and cT1, the timing of key milestones for the Company’s clinical assets, future plans or expectations for pemvidutide for the treatment of MASH, any meetings with the FDA, and the prospects for receiving regulatory approval or commercializing or selling any product or drug candidates, 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:
Lee Roth
Burns McClellan
Phone: 646-382-3403
lroth@burnsmc.com

Media Contact:
Savannah Valade
Real Chemistry
Altimmune@realchemistry.com

FAQ

What did Altimmune (ALT) announce about pemvidutide on December 19, 2025?

Altimmune announced positive 48‑week IMPACT Phase 2b topline results showing significant improvements in ELF, LSM, liver fat, ALT, and weight versus placebo.

How large were ELF and LSM improvements in the ALT 48‑week IMPACT trial?

ELF fell by 0.49 and 0.58 and LSM fell by 3.04 and 3.97 for 1.2 mg and 1.8 mg doses versus placebo.

What weight loss did pemvidutide produce in the ALT IMPACT trial at 48 weeks?

Participants lost 4.5% (1.2 mg) and 7.5% (1.8 mg) of body weight versus 0.2% for placebo at 48 weeks.

Did the FDA provide guidance for pemvidutide’s next steps after ALT’s 48‑week data?

Yes; Altimmune reported an End‑of‑Phase 2 FDA meeting that aligned on parameters for a registrational Phase 3 trial and permitted use of AIM‑MASH AI Assist.

When does Altimmune intend to start pemvidutide Phase 3 after the IMPACT results?

Altimmune intends to initiate the pemvidutide Phase 3 program in 2026.

How was pemvidutide tolerated in the 48‑week IMPACT trial in terms of discontinuations?

Adverse‑event discontinuations were 0% for 1.2 mg and 1.2% for 1.8 mg, versus 3.5% for placebo.