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

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 leastone protocol-specified conventional or advanced CD therapy

• Males and females of childbearing potential must meet protocol criteria forcontraception requirements

Exclusion Criteria:

• Current diagnosis of ulcerative colitis (UC) or indeterminate colitis, ischemiccolitis, infectious colitis, radiation colitis, microscopic colitis

• Participant with a history of >= 3 bowel resections (> 2 missing segments of the 5following segments: terminal ilelium, right colon, transverse colon, sigmoid andleft 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 toxicmegacolon

• Presence of abdominal or perianal abscess

• Presence of rectovaginal 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

• Past or current evidence of definite low-grade or high-grade colonic dysplasia oradenomas or neoplasia not completely removed

• History of malignancy within 5 years, with the exception of malignancies adequatelytreated with resection for non-metastatic basal cell or squamous cell cancer or insitu cervical cancer

• Evidence of infection with Clostridioides difficile (C. difficile; formerly known asClostridium difficile), cytomegalovirus (CMV), human immunodeficiency virus (HIV),Hepatitis B (HBV), Hepatitis C (HCV)

• Has evidence of active tuberculosis (TB), latent TB not successfully treated (perlocal guidance) or inadequately treated TB

• Has received protocol-specified prohibited medicines, including known exposure toany type of anti-TL1A therapy