Lilly starts two phase 3b trials pairing tirzepatide with mirikizumab in IBD
The studies will show whether adding a weight-lowering drug improves IBD control in patients whose obesity may blunt biologic response, but results are not expected until 2028 [1][2].
Eli Lilly has started two phase 3b trials that give tirzepatide, the molecule in Mounjaro and Zepbound, together with the biologic mirikizumab in adults who have inflammatory bowel disease and are also obese or overweight [1][2]. The studies test whether adding a weight-lowering drug helps patients whose excess weight may make biologic therapy work less well [1][2].
The ulcerative colitis trial, registered as NCT06937086, plans to enroll an estimated 350 adults with moderately to severely active ulcerative colitis and obesity or overweight [1]. Participants are followed to week 52, when researchers measure a combined primary endpoint: clinical remission plus a reduction in body weight of at least 10 percent [1].
The Crohn's disease trial, NCT06937099, plans an estimated 290 adults with moderately to severely active Crohn's disease and obesity or overweight [2]. Its primary endpoint uses a similar combination and adds endoscopic remission, which is judged by how the lining of the intestine looks during a colonoscopy [2].
Mirikizumab is an IL-23 inhibitor, a type of biologic that targets one of the immune pathways involved in gut inflammation [1][2]. Tirzepatide is the active ingredient in Mounjaro and Zepbound [1][2]. Both studies are phase 3b, a late stage of testing [1][2]. A composite endpoint means a result is judged on the included measures together, rather than on either one alone [1][2].
Obesity is associated with a worse response to biologic therapy in IBD, which is the stated rationale for testing the two drugs together [1][2]. Details such as dosing, study locations, and whether some participants receive a placebo instead of tirzepatide have not been reported [1][2], and no results have been released [1][2].
Why it matters for patients
For adults who have both IBD and obesity, the trials address a practical question: whether the drugs that calm gut inflammation work better when weight is treated at the same time [1][2]. If the combination helps, it could give doctors a way to address both conditions together. If it does not, patients and their doctors would still learn whether weight influences how well biologics perform [1][2].
The safety of combining the two drugs in this population has not been established [1][2]. Both trials enroll only adults with moderately to severely active disease who are also obese or overweight, so any findings would apply to that group first [1][2]. People whose IBD is mild, or who are not obese or overweight, are not the focus of these studies [1][2].
Results are years away, so no one can say yet whether tirzepatide adds benefit on top of mirikizumab or changes the side-effect profile of either drug [1][2].
What happens next
The registry lists estimated primary completion dates of April 2028 for the ulcerative colitis trial [1] and May 2028 for the Crohn's disease trial [2]. Those are targets and can shift. Whether the studies are currently enrolling, and how many sites are taking part, has not been reported [1][2].
Sources
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