Merck’s ulcerative colitis drug hits key goals in late-stage trial

Merck said tulisokibart met the main goal and key secondary goals in a phase 3 ulcerative colitis trial, giving the drug its first late-stage win in a disease market already crowded with established brands. In the ATLAS-UC induction-only study, patients reached clinical remission by the Modified Mayo Score at week 12, and Merck said the drug also improved the condition of the colon and reduced inflammation in tissue samples.

The company said no safety concerns were identified in the 12-week study, but it did not disclose the full numerical readout that would show how strong the result really was. Merck has not yet released remission rates, dose comparisons or placebo contrasts, leaving open the question of whether tulisokibart is materially more effective than current therapies or simply another option in a competitive class. Detailed results are due later at a scientific congress and will also be shared with regulators.

That uncertainty matters because ulcerative colitis is already treated by a long list of entrenched drugs, including Takeda’s Entyvio, AbbVie’s Skyrizi and Rinvoq, and Johnson & Johnson’s Tremfya. Older standards such as Humira and Stelara are also losing ground as biosimilars spread. Merck’s readout also arrives as the anti-TL1A race heats up: Teva and Sanofi reported positive phase 2b data for duvakitug in 2024 and later said maintenance results showed durable efficacy in February 2026, while Spyre Therapeutics reported positive phase 2 ulcerative colitis data for SPY002 in June 2026.

Tulisokibart, once known as PRA023 and MK-7240, came to Merck through its $10.8 billion acquisition of Prometheus Biosciences in 2023. Merck framed that deal as a way to deepen its immunology pipeline, and the latest ulcerative colitis result is the clearest validation yet of one of the assets it bought. The company said tulisokibart is now being tested in seven diseases, including Crohn’s disease, systemic sclerosis-associated interstitial lung disease, rheumatoid arthritis, psoriatic arthritis, radiographic axial spondyloarthritis and hidradenitis suppurativa.

The timing is also important for Merck’s broader business. The company has leaned heavily on oncology for growth, so a successful new inflammatory bowel disease drug could diversify revenue if the program continues to deliver. RBC Capital Markets has estimated that tulisokibart could reach the market in 2027 if later studies stay positive, while earlier phase 2 ARTEMIS-UC data suggested the drug may have durability as well, with roughly half of higher-dose patients achieving disease clearance after a year.