A Study to Assess the Efficacy and Safety of Induction and Maintenance Therapy With Afimkibart (RO7790121) in Participants With Moderately to Severely Active Crohn's Disease

Prior treatment

• Current diagnosis of ulcerative colitis (UC) or indeterminate colitis, ischemic colitis, infectious colitis, radiation colitis, microscopic colitis
• Has received protocol-specified prohibited medicines, including known exposure to any type of anti-TL1A therapy

Other illness

• Participant with a history of \>= 3 bowel resections (\> 2 missing segments of the 5 following segments: terminal ilelium, right colon, transverse colon, sigmoid and left colon, and rectum)
• Diagnosis of short gut or short bowel syndrome
• Presence of rectovaginal, enterovaginal, high output enterocutaneous fistula, enterovesical fistulas or perianal fistulas with \>3 openings
• Any past or current evidence of cancer of gastrointestinal tract, definite low-grade or high-grade colonic dysplasia
• History of non-gastrointestinal cancer, with the exception of adequately treated non-metastatic basal cell or squamous cell skin cancer or in situ cervical cancer
• Evidence of infection with Clostridioides difficile (C. difficile; formerly known as Clostridium difficile), cytomegalovirus (CMV), human immunodeficiency virus (HIV), Hepatitis B (HBV), Hepatitis C (HCV) during screening
• Has evidence of active tuberculosis (TB), latent TB not successfully treated (per local guidance) or inadequately treated TB

Other

• Presence of an ileostomy, colostomy or ileoanal pouch
• Participants with symptomatic bowel strictures, fulminant colitis, or toxic megacolon
• Presence of abdominal or perianal abscess
• Current diagnosis or suspicion of primary sclerosing cholangitis
• Pregnancy or breastfeeding, or intention of becoming pregnant during the study

• Confirmed diagnosis of CD
• Moderately to severely active CD
• Bodyweight \>= 40 kilogram (kg)
• Demonstrated inadequate response, loss of response and/or intolerance to at least one protocol-specified conventional or advanced CD therapy
• Males and females of childbearing potential must meet protocol criteria for contraception requirements