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

Altimmune, Inc., a late clinical-stage biopharmaceutical company developing therapies that address serious liver diseases, 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.

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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.

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“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. 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.

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Source- GlobeNewswire