PARIS — Shares of French biotechnology company Abivax surged Tuesday after fresh clinical trial data eased investor concerns about potential cancer risks tied to the company’s experimental ulcerative colitis treatment, clawing back the bulk of a steep selloff that had hammered the stock earlier this month.

The U.S.-listed stock climbed $32.81, or 34.12%, to $128.96 as of 9:47 a.m. EDT. In Paris, where Abivax is headquartered and primarily listed, shares were trading up roughly 36% at €113.30, after earlier touching gains as high as 36% intraday, according to multiple market trackers. The rally extends a recovery that began Monday evening, when U.S.-listed shares jumped 26.4% to 28% in extended trading immediately following the data release.

Tuesday’s surge comes almost exactly four weeks after Abivax shares collapsed by as much as 44% on June 2, when an earlier readout from the same trial identified seven distinct cancer diagnoses among patients taking the highest dose of the company’s lead drug, obefazimod. While investigators at the time assessed none of those cases as likely connected to the drug itself, the disclosure was enough to rattle markets and trigger one of the steepest single-session declines the stock had experienced.

The newly released data, covering the second part of Abivax’s Phase 3 ABTECT maintenance trial, gave investors a considerably larger and more reassuring safety picture. The expanded, combined safety database from the company’s Phase 2 and Phase 3 programs now spans the equivalent of 1,704 patient-years of drug exposure. Within that larger dataset, malignancies excluding non-melanoma skin cancer occurred at a rate of 0.35 events per 100 patient-years across all active treatment doses combined, falling squarely within the company’s expected background range of 0.30 to 0.70 cases typically seen in ulcerative colitis patients generally. Four cases of non-melanoma skin cancer were reported in the latest data, split evenly between the two dose arms, with all four occurring in patients who carried established risk factors such as older age, prior use of thiopurine medications, or a personal history of skin cancer. Two additional non-skin malignancies were reported in the higher 50-milligram dose group and were deemed unrelated to the drug.

Beyond the safety data, the update also offered encouraging efficacy results for patients who had struggled to respond to earlier treatment. Among patients who failed to respond during the trial’s initial induction phase, 37.2% achieved clinical remission and 34.5% reached endoscopic remission after 44 weeks of continued treatment on the 50-milligram dose of obefazimod. Among patients whose disease had relapsed after initially responding to a lower 25-milligram dose, escalating treatment to the 50-milligram dose helped restore clinical remission in 45.5% of cases.

Abivax Chief Executive Marc de Garidel described the results as a significant milestone for the drug’s development, characterizing the expanded dataset as substantially strengthening the company’s long-term safety database. Remo Panaccione, a professor of medicine and director of the Inflammatory Bowel Disease Clinic at the University of Calgary, offered an outside clinical perspective on the malignancy figures, noting that the observed rates were consistent with expected background rates for the patient population being studied.

Wall Street’s reaction to the update was broadly favorable. Piper Sandler said the results should help put to rest concerns that obefazimod could cause tumors, while analysts at Jefferies called the update supportive, though they cautioned that some generalist investors, as opposed to specialists and physicians closer to the data, might remain hesitant to fully embrace the stock given the lingering cancer signal and the company’s ongoing funding needs. Stifel maintained its buy rating and €115 price target on the stock, while Oddo BHF kept its outperform rating and €120 target, noting that while the new analyses did not constitute definitive proof of an absence of risk, they offered meaningfully more reassurance than the company’s earlier maintenance data readout. Several other firms, including Citizens, Barclays, Guggenheim, Truist and Morgan Stanley, have maintained buy or overweight ratings on the stock throughout the recent volatility.

Abivax confirmed it remains on track to submit a New Drug Application to the U.S. Food and Drug Administration for obefazimod in the fourth quarter of 2026, with a potential commercial launch widely expected in 2027 if the filing is approved. The company is also evaluating obefazimod as a potential treatment for Crohn’s disease, a related and similarly difficult-to-treat form of inflammatory bowel disease, with results from a mid-stage Phase 2b trial expected around mid-2027. Analysts have continued to describe obefazimod as a potential best-in-class treatment within the broader inflammatory bowel disease category, a market collectively worth billions of dollars annually.

The stock’s dramatic swings over the past month reflect both the high-stakes nature of single-asset clinical-stage biotech investing and the considerable run Abivax has had over the past year more broadly. Shares gained nearly 1,700% during 2025, pushing the company’s market capitalization to roughly €8 billion even after accounting for this month’s volatility. Heading into Tuesday’s session, shares had been down about 14% year-to-date, a deficit that has now narrowed to roughly 6% following the rally. Abivax has also long been viewed by market watchers as a potential acquisition target, with persistent, unverified speculation that one or more major pharmaceutical companies have considered a takeover of the Paris-based biotech, a dynamic that some investors said factored into Tuesday’s enthusiastic reaction alongside the underlying clinical data itself.

Tuesday’s rally also came against a generally constructive backdrop for European equities, with the pan-European Stoxx 600 index on track for its strongest quarterly performance since October 2020, and Abivax’s home index, the CAC 40, trading modestly higher on the day. Even so, market commentators were careful to note that the scale of Abivax’s single-session move was driven overwhelmingly by company-specific news rather than broader market tailwinds, underscoring just how heavily clinical-stage biotech valuations can swing on individual trial readouts, in either direction, for a company whose fortunes remain closely tied to the fate of a single experimental drug.