8-K: Altimmune's Pemvidutide Shines in MASH Trial

Altimmune, Inc. announced positive 48-week topline results from its IMPACT Phase 2b trial of pemvidutide for MASH, showing statistically significant improvements in fibrosis markers and weight loss.

Summary

• Positive 48-week topline results from the IMPACT Phase 2b trial of pemvidutide for metabolic dysfunction-associated steatohepatitis (MASH) were announced.
• Treatment with pemvidutide achieved statistically significant improvements in key non-invasive tests (NITs) for fibrosis, including Enhanced Liver Fibrosis (ELF) and Liver Stiffness Measurement (LSM), across treatment arms versus placebo.
• Data exhibited continued reductions in ELF and LSM from week 24, providing evidence of sustained antifibrotic activity with both 1.2 mg and 1.8 mg doses.
• Additional weight loss was observed with the 1.8 mg dose, reaching 7.5% at 48 weeks, with no evidence of plateauing.
• The 48-week data maintained a favorable tolerability profile, with lower discontinuation rates due to adverse events (0% for 1.2 mg, 1.2% for 1.8 mg) compared to placebo (3.5%).
• Statistically significant reductions were also achieved in other non-invasive measures of liver health and hepatic inflammation, including liver fat content (45.2% for 1.2 mg, 54.7% for 1.8 mg vs. 8.2% for placebo), alanine aminotransferase (ALT), and corrected T1 (cT1).
• An End-of-Phase 2 meeting with the FDA was held on December 11, 2025, resulting in alignment on a pathway forward to a registrational Phase 3 trial for pemvidutide in MASH patients with moderate to advanced liver fibrosis.
• The FDA indicated openness to incorporating AIM-MASH AI Assist, an FDA-qualified AI pathology tool, into the Phase 3 trial.
• Altimmune intends to evaluate multiple doses, including 2.4 mg, in the Phase 3 trial and will seek scientific advice from European regulators.
• Since September 30, 2025, and through December 19, 2025, Altimmune sold 13,547,341 shares of common stock for net proceeds of approximately $54.6 million through its at-the-market (ATM) offering programs.

Sentiment

Score: 9

Explanation: The filing reports overwhelmingly positive clinical trial results for a key drug candidate, successful FDA alignment for Phase 3, and a strong safety profile, indicating significant progress and potential for the company.

Positives

• Statistically significant reductions in ELF: -0.49 (1.2 mg) and -0.58 (1.8 mg) vs. +0.16 (placebo) (p<0.0001 for both doses).
• Statistically significant reductions in LSM: -3.04 (1.2 mg, p<0.05) and -3.97 (1.8 mg, p<0.001) vs. -0.03 (placebo).
• High proportion of participants achieved both a 0.5 reduction in ELF and a 30% reduction in LSM: 27.8% (1.2 mg, p<0.001) and 32.4% (1.8 mg, p<0.0001) vs. 3.2% (placebo).
• Statistically significant reductions in liver fat content: 45.2% (1.2 mg) and 54.7% (1.8 mg) vs. 8.2% (placebo) (p<0.0001).
• Statistically significant reductions in ALT: -37.8 IU/L (1.2 mg) and -37.4 IU/L (1.8 mg) vs. -10.3 IU/L (placebo) (p<0.0001 for both doses).
• Statistically significant reductions in cT1: -124 ms (1.2 mg) and -140 ms (1.8 mg) vs. -21 ms (placebo) (p<0.0001 for both doses).
• Significant weight loss: 4.5% (1.2 mg) and 7.5% (1.8 mg) vs. 0.2% (placebo) (p<0.0001 for both doses), with no plateauing at 48 weeks for the 1.8 mg dose.
• Favorable tolerability profile maintained with low adverse event discontinuation rates: 0% (1.2 mg) and 1.2% (1.8 mg) vs. 3.5% (placebo).
• No serious or severe adverse events related to treatment were reported.
• Productive End-of-Phase 2 meeting with the FDA resulted in alignment on the pathway to a registrational Phase 3 trial.
• FDA indicated openness to incorporating AIM-MASH AI Assist, the first FDA-qualified AI pathology tool for MASH clinical trials, into the Phase 3 trial.

Risks

• The success, cost, and timing of the company's product candidate development activities and planned clinical trials.
• The company's ability to execute on its strategy.
• Positive results from any clinical studies may not necessarily be predictive of the results of future or ongoing clinical studies.
• 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, regulatory developments in the United States and foreign countries.
• The company's ability to manufacture clinical trial materials on the timelines anticipated.
• The company's ability to fund operations.
• 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.
• Subject baseline characteristics which may vary and impact the success of future trials.

Future Outlook

Altimmune plans to initiate a registrational Phase 3 trial for pemvidutide in MASH patients with moderate to advanced liver fibrosis in 2026, evaluating multiple doses including 2.4 mg, and incorporating the FDA-qualified AIM-MASH AI Assist tool. The company will also seek scientific advice from European regulators to inform the final Phase 3 protocol. Additionally, Altimmune expects topline data from the RECLAIM Phase 2 AUD trial in 2026 and completion of the RESTORE Phase 2 ALD trial in 2027.

Management Comments

• "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." Mazen Noureddin, M.D., IMPACT trial principal investigator.
• "I am encouraged by the dose response observed and the performance of the 1.8 mg arm and am eager to see this differentiated therapeutic candidate advance into Phase 3 evaluation." Mazen Noureddin, M.D.
• "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 pemvidutides differentiation and potential to be a meaningful treatment option for the MASH patient community." Vipin Garg, Ph.D., Chief Executive Officer of Altimmune.

Industry Context

Metabolic dysfunction-associated steatohepatitis (MASH) is a progressive liver disease with significant unmet medical need, as currently approved treatment options often do not fully address both the metabolic drivers and fibrosis that pose long-term risks. Pemvidutide, as a balanced 1:1 glucagon/GLP-1 dual receptor agonist, is positioned to address both liver-specific and metabolic aspects of the disease. The positive 48-week data, coupled with a favorable tolerability profile, suggest pemvidutide could be a differentiated and meaningful treatment option in this challenging therapeutic landscape, potentially offering a comprehensive solution where existing therapies may fall short.

Comparison to Industry Standards

• Pemvidutide (GLP-1/GCG) 1.8 mg achieved a placebo-adjusted ELF change from baseline of -0.74 at 48 weeks, which compares favorably to Resmetirom (THR-β) 100 mg (-0.61 at 52 weeks, Phase 3), Efruxifermin (FGF21) 50 mg (-0.6 at 52 weeks, Phase 2b), Semaglutide (GLP-1) 2.4 mg (-0.24 at 72 weeks, Phase 3), and Tirzepatide (GLP-1/GIP) 15 mg (-0.65 at 96 weeks, Phase 2).
• Pemvidutide (GLP-1/GCG) 1.8 mg achieved a placebo-adjusted LSM change from baseline of -3.94 kPa at 48 weeks, which compares to Resmetirom (THR-β) 100 mg (-3.48 kPa at 52 weeks, Phase 3), Efruxifermin (FGF21) 50 mg (-2.2 kPa at 52 weeks, Phase 2b), Semaglutide (GLP-1) 2.4 mg (-3.02 kPa at 72 weeks, Phase 3), and Tirzepatide (GLP-1/GIP) 15 mg (-6.6 kPa at 96 weeks, Phase 2).
• It is important to note that no head-to-head studies have been conducted, and cross-trial comparisons must be interpreted with caution due to differences in patient populations, study designs, and other factors.

Stakeholder Impact

• Shareholders: Positive clinical results and a clear path to Phase 3 could increase investor confidence and potentially lead to an appreciation in share price. The ATM sales provide capital for ongoing operations but also result in some dilution.
• Patients (MASH): Pemvidutide shows strong promise as a differentiated and effective treatment option for a serious liver disease with high unmet medical need, potentially offering significant improvements in liver health and weight management.
• Employees: Continued progress in clinical development and a clear strategic pathway enhance job security and the company's long-term viability.
• Regulatory Authorities: Successful engagement with the FDA and the potential integration of AI tools demonstrate a commitment to rigorous development and innovation in regulatory processes.

Next Steps

• Receive final minutes from the End-of-Phase 2 meeting with FDA in January 2026.
• Seek scientific advice from European regulators to inform the final Phase 3 protocol.
• Initiate registrational Phase 3 trial for pemvidutide in MASH in 2026.
• Evaluate multiple doses, including 2.4 mg, in the Phase 3 trial.
• Integrate AIM-MASH AI Assist into the Phase 3 trial.
• Expect RECLAIM Phase 2 AUD trial topline data in 2026.
• Expect RESTORE Phase 2 ALD trial enrollment completion in 2026.
• Expect RESTORE Phase 2 ALD trial completion in 2027.

Key Dates

Recommendation

The 48-week IMPACT Phase 2b data for pemvidutide in MASH are exceptionally strong, demonstrating statistically significant improvements across multiple key non-invasive markers of fibrosis, liver health, and substantial weight loss, all while maintaining a favorable tolerability profile. The successful End-of-Phase 2 meeting with the FDA, including alignment on a registrational Phase 3 pathway and openness to incorporating an AI pathology tool, significantly de-risks the development program. These results position pemvidutide as a highly differentiated and competitive candidate in a market with substantial unmet medical need, suggesting significant future value creation for Altimmune. The ATM sales provide capital for continued development, supporting the strong outlook.

Keywords

Altimmune, pemvidutide, MASH, metabolic dysfunction-associated steatohepatitis, Phase 2b, IMPACT trial, glucagon/GLP-1 dual receptor agonist, liver fibrosis, weight loss, FDA, clinical trial, biopharmaceutical, drug development, non-invasive tests, ELF, LSM, liver fat, ALT, cT1, ATM offering, equity distribution