Abivax (NASDAQ: ABVX) experienced a sharp decline in after-hours trading on Monday, with its American depositary shares falling 33.7% to $86.01, despite the release of positive late-stage clinical data for its lead ulcerative colitis drug, obefazimod. The stock had closed the regular session at $129.69, down 2.2% on the day.
Phase 3 Trial Results
The French biotech announced that its Phase 3 ABTECT maintenance study met the primary endpoint, with both the 25 mg and 50 mg once-daily doses of obefazimod achieving clinical remission at Week 44. Specifically, 50.8% of patients on the 25 mg dose and 51.3% on the 50 mg dose reached clinical remission, compared to just 10.4% for the placebo group. The drug also met key secondary endpoints, including endoscopic improvement, which measures visible tissue healing in the colon.
Safety Profile
Abivax reported no new safety signals and no deaths in the trial. Treatment-emergent adverse events occurred in 58.0% of patients on the 25 mg dose and 71.8% on the 50 mg dose, versus 50.0% for placebo. The higher rate of side effects at the 50 mg dose may be a concern for investors, as it could influence the drug's eventual label and prescribing practices.
Regulatory Path and Timeline
With these results, Abivax plans to file a New Drug Application (NDA) with the U.S. Food and Drug Administration (FDA) in late Q4 2026. The NDA is the formal request for approval to market the drug in the United States. The company expects to have sufficient cash to fund operations into Q4 2027, with cash, cash equivalents, and short-term investments totaling €491.6 million as of March 31, 2026.
Market Context and Competition
Obefazimod, if approved, will enter a competitive market for moderate-to-severe ulcerative colitis. Existing oral therapies include AbbVie's (NYSE: ABBV) Rinvoq and Pfizer's (NYSE: PFE) Velsipity, both of which have FDA approval. Takeda's (NYSE: TAK) Entyvio, available in intravenous and injectable forms, is another major player. The market is also crowded with biologic therapies, making differentiation crucial for Abivax.
Investor Sentiment and Trading Dynamics
The sharp after-hours decline suggests that positive clinical data alone is not sufficient to sustain the stock's valuation, especially after a significant run-up in 2025. Investors are likely weighing the competitive landscape, the higher side-effect profile at the 50 mg dose, and the uncertainties of the regulatory review and launch costs. Additionally, takeover speculation has been a factor, with Abivax previously denying reports of interest from AstraZeneca (NASDAQ: AZN) and Eli Lilly (NYSE: LLY).
Financial Outlook
Abivax reported a first-quarter net loss of €48.5 million, with R&D expenses increasing to €49.5 million. The company's next major catalysts include its half-year results on September 21, 2026, and data from a Crohn's disease trial expected in mid-2027. The stock's performance will depend on how traders interpret Monday's data in the context of the overall market and competitive dynamics.
