AbiVax falls as safety worries cloud ‘landmark’ immune drug results

An article from Dive Brief AbiVax falls as safety worries cloud ‘landmark’ immune drug results A handful of cancer cases reported among treatment recipients overshadowed efficacy results analysts described as “best-in-disease” and sent shares down more than 30%. Published June 2, 2026 Ben Fidler Lead Editor Share Copy link Email LinkedIn X/Twitter Facebook Print License Add us on Google Dive Brief: Shares of Abivax tumbled Tuesday despite what the company described as “landmark” Phase 3 data, as safety concerns clouded findings showing its experimental therapy appeared more effective than other marketed drugs for inflammatory bowel disease. After 44 weeks, two different doses of its drug, obefazimod, were associated with placebo-adjusted clinical remission rates of about 39% and 40%, respectively, in patients with moderately to severely active ulcerative colitis. Those figures far surpassed investor expectations and represented what some analysts described as “best-in-disease” efficacy. However, investigators also detected malignancies in a few drug recipients treated with a higher dose of AbiVax’s drug. AbiVax said those events were deemed unrelated to treatment, weren’t “clustered” around a specific organ, and that it aims to file for approval in the fourth quarter. Company shares fell by a third on Tuesday, however, wiping out billions in market value. Dive Insight: AbiVax has had a meteoric rise over the last year thanks to the progress of obefazimod. The drug works differently than other available treatments for inflammatory bowel disease, boosting the expression of an important immune response regulator called miR-124. That approach is meant to dampen the inflammation associated with IBD, but without broadly suppressing the body’s defenses. As a once-daily pill, obefazimod could offer a convenience advantage over many approved IBD therapies, too. Large drugmakers have scooped up several makers of oral immune disease medicines in recent years on the potential that these kinds of drugs might match the potency of injectable therapies. AbiVax’s data has suggested obefazimod may even be superior to injectable counterparts, which typically show placebo-adjusted remission rates in the range of 19% to 32%, wrote Stifel analyst Damien Choplain in a Tuesday client note. Shares once worth less than $10 apiece closed on Monday at nearly $130 amid expectations obefazimod could upend IBD treatment or that AbiVax — a rumored buyout target — might be acquired along the way. The Phase 3 findings supported that potential, with treatment producing remission rates of around 51% at both tested doses, compared to about 10% for placebo recipients. Those findings met the study’s main objective, “clearly exceeded expectations,” and separate obefamizod from competitors, wrote Leerink Partners’ Thomas Smith. The drug achieved all of its key secondary study goals, too. But the detection of a handful of malignancies of the prostate, breast and skin appears to have spooked Wall Street investors. While rare, sporadic in nature and of unclear cause, those events “introduced uncertainty” and represent a signal that “cannot be ignored,” Choplain wrote. Both analysts rallied to AbiVax’s defense. Smith noted how widely used IBD drugs like Stelara and Entyvio carry language on their prescribing information that notes the theoretical risk of a malignancy. Even if the Food and Drug Administration were to require similar labeling for obefamizod, the drug would remain “commercially competitive” given the “compelling” efficacy results and sales trajectory of other medications, he added. Choplain also noted how AbbVie’s Rinvoq, a different type of oral IBD medicine, has a “boxed warning” for malignancy but still generated $8.3 billion in sales last year. The drug’s approval is “likely,” assuming the full data confirms “no causal signal,” he added. Add us on Google Share Copy link Email LinkedIn X/Twitter Facebook Print purchase licensing rights Filed Under: Clinical Trials