This goal of this sub-study is to learn how safe and tolerable the study drug, aletekitug (anti-IL-18), in participants with moderately to severely active ulcerative colitis (UC). This study is the sub-study of the platform trial.
Diagnosis of UC for greater than or equal (>=) 3 months before screening. Appropriate documentation of endoscopy and biopsy results consistent with the diagnosis of UC must be available.
Active UC with a modified Mayo score (mMS) of 5 to 9 points and endoscopy sub score of 2 to 3 within 14 days before baseline biopsy collection.
Active disease beyond the rectum (greater than [>]15 centimeter [cm] of active disease from the anal verge at the screening colonoscopy).
Documentation of a surveillance colonoscopy (performed according to local standard) within 12 months before screening (may be performed during screening) for participants with pancolitis of >8 years duration or left-sided colitis of >12 years duration, or primary sclerosing cholangitis
Participants with current diagnosis of Crohn's disease (CD) or Inflammatory bowel disease-unclassified (IBD-U) or a history of radiation colitis, microscopic colitis or ischemic colitis. Have currently known complications of UC such as fulminant colitis, or toxic megacolon, stoma, or stricture/stenosis within the small bowel or colon.
Have prior history of dysplasia of the gastrointestinal tract or found to have dysplasia, other than completely removed low-grade dysplastic lesions, in any biopsy performed during the screening endoscopy.
Have a history of malignant neoplasm within the last 5 years.
Have history of lymphoproliferative disorder, including lymphoma, or signs and symptoms suggestive of possible lymphoproliferative disease