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

This Phase III, multicenter, double-blind, placebo-controlled treat-through study will evaluate the efficacy and safety of induction and maintenance therapy with Afimkibart (also known as RO7790121) in participants with moderately to severely active Crohn's disease (CD).

Inclusion Criteria: * 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 Exclusion Criteria: * Current diagnosis of ulcerative colitis (UC) or indeterminate colitis, ischemic colitis, infectious colitis, radiation colitis, microscopic colitis * 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 an ileostomy, colostomy or ileoanal pouch * Participants with symptomatic bowel strictures, fulminant colitis, or toxic megacolon * Presence of abdominal or perianal abscess * Presence of rectovaginal, enterovaginal, high output enterocutaneous fistula, enterovesical fistulas or perianal fistulas with \>3 openings * Current diagnosis or suspicion of primary sclerosing cholangitis * Pregnancy or breastfeeding, or intention of becoming pregnant during the study * 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 * Has received protocol-specified prohibited medicines, including known exposure to any type of anti-TL1A therapy