Merck's anti-TL1A drug hits main goal in ulcerative colitis trial, though data gaps temper analyst enthusiasm

Merck & Co (MRK) said that its experimental drug tulisokibart met the main goal and key secondary goals in a late-stage trial of patients with ulcerative colitis, a chronic inflammatory bowel disease.

Ulcerative colitis causes long-lasting inflammation and ulcers in the innermost lining of the large intestine and rectum. At twelve weeks, the trial showed clinical remission in symptoms of the disease among patients who received the drug. Merck said those patients also showed signs of improvement in the condition of their colon and reduced inflammation in tissue samples over the same period.

Tulisokibart is designed to block TL1A, a protein involved in immune activity and the buildup of scar-like tissue.

Analysts described the results as encouraging but pointed to a notable absence of quantitative detail. Geoff Meacham, an analyst at Citi, said Merck had not disclosed how many patients achieved remission, how different doses performed, how the drug compared with placebo, or how it worked across specific patient groups. He said the lack of data limited competitive read-through against rival treatments for now.

Trung Huynh, an analyst at RBC Capital Markets, said the results marked the first positive late-stage data for an anti-TL1A drug, giving Merck an early lead in a drug class he described as a compelling therapeutic option for inflammatory bowel disease. Huynh forecast a launch in 2027 and annual sales of $5.2bn by 2034.

Merck said results from the trial would be presented alongside data from an ongoing maintenance study at an upcoming scientific congress. The company is testing tulisokibart across seven diseases in total, including ulcerative colitis.