This is a multinational, multicenter, randomized, double-blind, placebo-controlled, Phase 3 induction study to evaluate the efficacy and safety of duvakitug in participants with moderately to severely active Ulcerative Colitis (UC). Study details include:

The study duration may be up to 35 weeks with:

• Screening period
• 12-week Sub-Study 1 (Single-Arm Open-Label Feeder Induction) or Sub-Study 2 (Pivotal Induction)
• 12-week Sub-Study 3 (Extended Induction for non-responders)
• 45 days follow-up visit for participants who do not enroll into the maintenance study (EFC18359)

The treatment duration will be up to 12 weeks in each sub-study. The number of scheduled on-site visits will be up to 8 for the Sub-Study 1 and Sub Study 2 or a maximum of 15 visits for participants completing extended induction.

Inclusion Criteria:

• Participants aged ≥18 and ≤80 years of age at Screening. Where permitted locally, participants 16 to <18 years of age who meet the definition of Tanner Stage 5 for development
• Confirmed diagnosis of moderately to severely active UC for at least 3 months prior to Baseline
• Demonstrated inadequate response, have shown loss of response or intolerance to conventional therapies or advanced therapies

Exclusion Criteria:

• Participants with Crohn's Disease (CD), indeterminate colitis
• Current diagnosis of Ulcerative Proctitis
• Participants with surgical bowel resection within the past 3 months prior to Baseline, or a history of >3 bowel resections
• Prior or current high-grade gastrointestinal (GI) dysplasia
• Participants on treatment with but not on stable doses of conventional therapies prior to baseline
• Participants with prohibited medications or therapies prior to baseline
• Participants with previous exposure to anti-TL1A investigational therapy The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org