A Study on the Safety of TAK-279 and Whether it Can Reduce Inflammation in the Bowel of Participants With Moderately to Severely Active Crohn's Disease

Crohn's disease (CD) is a long-lasting condition causing inflammation that can affect any part of the gut. The purpose of this study is to evaluate the efficacy and safety of TAK-279 versus placebo in participants with moderately to severely active Crohn's disease (CD). The main aim of this study is to learn if the 3 different doses of TAK-279 reduce bowel inflammation and ulcers in the bowel compared to the placebo after 12 weeks of treatment. Another aim is to compare any medical problems that participants have when they take TAK-279 or placebo and how well the participants tolerate medical problems. An endoscopy will be used to check the bowel for inflammation. The participants will be treated with TAK-279 for 52 weeks (1 year). During the study, participants will visit their study clinic 15 times.

The drug being tested in this study is TAK-279. TAK-279 is being tested to treat participants with moderately to severely active Crohn's disease. The study will look at the efficacy and safety of TAK-279. The study will enroll approximately 268 participants. During the Induction Period participants will be randomly assigned to one of the following treatment groups in a ratio of 1:1:1:1 to receive TAK-279 or placebo which will remain undisclosed to the participant and study doctor during the study (unless there is an urgent medical need): 1. TAK-279 Dose 1 2. TAK-279 Dose 2 3. TAK-279 Dose 3 4. Placebo This multi-center trial will be conducted globally. The overall study duration is approximately 60 weeks including a 4-week safety follow-up period.

Inclusion Criteria: 1. Male or female aged 18-75 years old with diagnosis of CD for at least 30 days. In South Korea, the age requirement for adult participants is \>=19 years of age. 2. Confirmed diagnosis of moderately to severely active CD assessed by SES-CD and CDAI. 3. Participants must have had an inadequate response to, loss of response to, or intolerance to at least one or more conventional, biologic, or advanced therapy for CD. Exclusion Criteria: 1. Participants with indeterminate colitis, microscopic colitis, ischemic colitis, infectious colitis, radiation colitis, and diverticular disease associated with colitis, and/or ulcerative colitis. 2. Have complications of CD that might require surgery during the study. 3. Participants with a current ostomy. 4. Participants who have failed 3 or more classes of advanced therapies.