■ReadoutUS26 Jun 20251 min read
Pemvidutide clears liver inflammation in phase 2 but misses on scarring
Many more patients saw their MASH resolve on drug than on placebo, but the fibrosis endpoint was not statistically significant, and the stock halved.
Holds at Phase 2 Mixed or neutral: news, but no net change in prospects.
The readHalf a win. Clearing inflammation is real progress, but regulators and investors count fibrosis, and 24 weeks is short to move scar tissue. The 48-week data matter more than the headline did.
The readout
IMPACT tested pemvidutide against placebo in adults with MASH (metabolic dysfunction-associated steatohepatitis) and liver fibrosis, using liver biopsies at 24 weeks. Altimmune reported that MASH resolution without worsening of fibrosis was reached in roughly three times as many patients on the higher dose as on placebo. The second primary endpoint, improvement in fibrosis without worsening of MASH, was numerically better on drug but did not reach statistical significance.
Why the market reacted
MASH drugs are judged on fibrosis because scarring is what leads to cirrhosis and liver failure. Competitors that combine GLP-1 with other mechanisms have shown fibrosis effects, so a miss on that endpoint, even a narrow one, hurt. Altimmune’s share price fell by about half on the day.
What we mark
- Stage stays at phase 2.
- Signal flat: one primary endpoint met, one missed.
- Weight loss in the trial was modest compared with obesity-focused drugs, which the company said is expected at these doses and duration.
Biopsy endpoints are noisy. Two pathologists reading the same slide can disagree, which makes small differences hard to prove.
48-week IMPACT results and the end-of-phase-2 talks with the FDA.
Primary sourceAltimmune press release, IMPACT phase 2b topline, June 2025
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