Altimmune Shares Plunge 60% Despite Positive MASH Trial Results as Fibrosis Endpoint Falls Short
Key Insights
Altimmune's stock crashed over 60% after its Phase 2b IMPACT trial of pemvidutide for MASH (search) showed mixed results, with strong MASH resolution but insufficient fibrosis (search) improvement.
The drug achieved statistically significant MASH (search) resolution in 59.1% of patients at 1.2 mg dose versus 19.1% on placebo, along with meaningful weight loss of up to 6.2%.
Despite meeting the primary endpoint, investors were disappointed by the lack of statistical significance in fibrosis (search) reduction, a critical benchmark for MASH (search) treatment success.
Altimmune's stock (NASDAQ: ALT) suffered a devastating 60-64% decline in pre-market trading following the announcement of mixed results from its Phase 2b IMPACT trial evaluating pemvidutide for metabolic dysfunction-associated steatohepatitis (search) (MASH (search)). While the drug demonstrated promising efficacy in MASH resolution and weight loss, it failed to achieve statistical significance in fibrosis (search) improvement, a critical endpoint that spooked investors despite the trial meeting its primary objective.
Trial Results Show Promise Despite Market Reaction
The IMPACT Phase 2b trial successfully met its primary endpoint of MASH (search) resolution without worsening liver fibrosis (search) at 24 weeks. The results showed impressive efficacy rates, with 59.1% of patients receiving the 1.2 mg dose achieving MASH resolution compared to only 19.1% on placebo. The 1.8 mg dose demonstrated a 52.1% resolution rate, with both doses showing statistical significance well above expectations.
Beyond liver health improvements, pemvidutide delivered substantial weight loss benefits, positioning it alongside other GLP-1 class medications. Patients experienced 5.0% weight loss at the 1.2 mg dose and 6.2% at the 1.8 mg dose, compared to just 1.0% in the placebo group.
Fibrosis Endpoint Creates Investor Concerns
The market's harsh reaction centered on the drug's performance in fibrosis (search) reduction, a major treatment goal in MASH (search) therapy. While an AI-assisted analysis revealed that 30.6% of patients achieved ≥60% reduction in fibrosis compared to 8.2% on placebo, this improvement did not reach statistical significance in the primary analysis. This shortfall in a key benchmark for MASH treatment success overshadowed the positive results in other areas.
Market Impact and Trading Activity
The stock opened at $2.96 and traded between $2.91 and $3.83 on exceptionally heavy volume of 75.5 million shares, far exceeding the average daily volume of 2.9 million shares. The dramatic decline brought shares close to their 52-week low of $2.91, representing a significant retreat from the 52-week high of $11.16.
As of the latest trading, Altimmune shares were priced at $7.71, though this represents the stock's position before the trial results announcement. The market capitalization is estimated between $558 million to $625 million.
Analyst Outlook Remains Optimistic
Despite the severe market reaction, Wall Street analysts maintain a "Strong Buy" rating on Altimmune stock, suggesting potential upside of nearly 190% from current price levels. This optimistic outlook assumes pemvidutide can regain investor confidence in subsequent trials and regulatory interactions.
Understanding MASH and Treatment Landscape
MASH (search), formerly known as NASH (search) (Non-Alcoholic Steatohepatitis), represents a serious form of fatty liver disease characterized by fat accumulation in the liver that causes inflammation and liver cell damage. The condition can progress to fibrosis (search), cirrhosis (search), or liver cancer (search), making effective treatments a significant unmet medical need with no currently approved therapies available.
Next Steps and Regulatory Path
Altimmune plans to conduct an investor webcast to discuss the trial results and outline future development plans. The company intends to meet with the FDA for an End-of-Phase 2 meeting by late 2025 to discuss the regulatory pathway forward. A Phase 3 trial remains under consideration, depending on regulatory feedback and strategic planning.
The mixed trial results highlight the challenges in developing effective MASH (search) treatments, where multiple endpoints must be addressed to achieve comprehensive therapeutic benefit. While pemvidutide showed clear efficacy in MASH resolution and weight management, the fibrosis (search) endpoint remains a critical hurdle that will likely influence the drug's future development strategy and commercial potential.