Shares of Altimmune Inc (NASDAQ:ALT) tumbled 55% on Thursday after the company reported mixed results from a mid-stage trial of its experimental drug pemvidutide for metabolic dysfunction-associated steatohepatitis (MASH).
The Phase 2b study met one of its primary endpoints, with pemvidutide achieving statistically significant resolution of MASH without worsening of fibrosis at 24 weeks. However, the drug failed to show statistically significant improvement in liver fibrosis, the more challenging endpoint, compared to placebo.
In the intention-to-treat (ITT) population, MASH resolution was observed in 59.1% and 52.1% of patients receiving pemvidutide 1.2 mg and 1.8 mg, respectively, versus 19.1% for placebo.
But fibrosis improvement without worsening of MASH was achieved in 31.8% and 34.5% of patients, compared with 25.9% in the placebo group — a difference that did not reach statistical significance.
Altimmune plans to proceed to a Phase 3 program after an End-of-Phase 2 meeting with the US Food and Drug Administration in the fourth quarter of 2025.
Analysts at Jefferies noted that while the lack of a statistically significant improvement in fibrosis may disappoint some investors, the broader dataset supports continued development.
Altimmune said it will follow participants through 48 weeks to assess additional endpoints and explore whether longer treatment duration or higher dosing could produce greater fibrosis benefits.