A Study to Assess the Efficacy and Safety of Subcutaneous Induction Therapy With Afimkibart in Participants With Moderately to Severely Active Ulcerative Colitis

Inclusion Criteria: * Confirmed diagnosis of UC. * Moderately to severely active UC assessed by modified Mayo Score (mMS). * Bodyweight \>= 40 kilogram (kg). * Up to date with colorectal cancer (CRC) screening performed according to local standards. * Demonstrated inadequate response, loss of response and/or intolerance to at least one protocol-specified conventional or advanced UC therapy. * Females of childbearing potential must meet protocol criteria for contraception requirements. Exclusion Criteria: * Currently known complications of UC (e.g. fulminant colitis, toxic megacolon). * Current diagnosis of Crohn's disease (CD) or indeterminate colitis, microscopic colitis, ischemic colitis, infectious colitis, radiation colitis. * Presence of an ostomy or ileoanal pouch. * 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 or adenomas or neoplasia not completely removed. * History of malignancy within 5 years, with the exception of malignancies adequately treated with resection for non-metastatic basal cell or squamous cell 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). * 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.