A Sub Study to Investigate the Safety and Tolerability of Aletekitug in Participants With Moderate To Severe Ulcerative Colitis

Inclusion Criteria: * 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 * Demonstrated an inadequate response to, loss of response to, or intolerance to conventional therapy (e.g., oral 5- aminosalicyclic acid \[5-ASA\] compounds, corticosteroids, thiopurines). * May have been receiving a conventional therapy if the prescribed dose has been stable for the required time period before the screening endoscopy. * Must meet contraception requirements if a female participant is a woman of childbearing potential (WOCBP) Exclusion Criteria: * 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 …