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

This Phase III, multicenter, double-blind, placebo-controlled study will evaluate the efficacy and safety of induction 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 * Participants with symptomatic bowel strictures, fulminant colitis, or toxic megacolon * 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