A Maintenance Study to Investigate the Efficacy and Safety of Duvakitug in Participants With Moderately to Severely Active Ulcerative Colitis

Pivotal Maintenance Sub-Study Cohort 1: Proportion of participants with endoscopic improvement.

Endoscopic improvement is defined as mMES of 0 or 1 (score of 1 excludes friability). Endoscopies were assessed by a blinded central reader and scored according to the following scale: 0 = Normal or inactive disease; 1 = Mild disease (erythema, decreased vascular pattern); 2 = Moderate disease (marked erythema, lack of vascular pattern, any friability, erosions); 3 = Severe disease (spontaneous bleeding, ulceration).

Time frame: Week 40

Pivotal Maintenance Sub-Study Cohort 1: Proportion of participants achieving histologic endoscopic mucosal improvement.

Histological endoscopic mucosal improvement is defined as MES of 0 or 1 without the evidence of friability and Geboes Score ≤3.1. The Geboes score has 6 grades: Grade 0, structural change only; Grade 1, chronic inflammation; Grade 2, lamina propria neutrophils and eosinophils; Grade 3, neutrophils in epithelium; Grade 4, crypt destruction; and Grade 5, erosions or ulceration.

Time frame: Week 40

Pivotal Maintenance Sub-Study Cohort 1: Proportion of participants with corticosteroid-free clinical remission.

Time frame: Week 40

Proportion of participants with no bowel urgency.

The NRS for bowel urgency is a patient-reported tool designed to measure the severity of bowel urgency-the sudden or immediate need to have a bowel movement-experienced in the past 24 hours. This tool utilizes an 11-point scale for evaluation, where 0 represents "no urgency" and 10 signifies the "worst possible urgency".

Time frame: Week 40

Pivotal Maintenance Sub-Study Cohort 1: Change from Baseline in PROMIS-Fatigue Short Form 7a T-score.

The PROMIS Fatigue Short Form 7a uses a 5-point Likert scale for each of its 7 items, resulting in a raw score range of 7 to 35. This raw score is then converted into a T-score, with a mean of 50 and a standard deviation of 10, based on US national norms. Higher Tscores indicate greater fatigue.

Time frame: Baseline, Week 40

Pivotal Maintenance Sub-Study Cohort 1: Proportion of participants with endoscopic remission.

Endoscopic remission is defined as mMES of 0.

Time frame: Week 40

Pivotal Maintenance Sub-Study Cohort 1: Proportion of participants achieving clinical remission by mMS, in the subset of participants who achieved clinical remission by mMs at the end of induction period (maintenance of clinical remission).

Clinical response is defined as a decrease from baseline in the mMS of ≥2 points and at least a 30% reduction from baseline, and a decrease in RB subscore of ≥1 or an absolute RB subscore of 0 or 1. Mayo Score is a composite index designed to measure UC disease activity. The score ranges from 0 to 9 with higher scores indicating greater disease severity.

Time frame: Week 40

Pivotal Maintenance Sub-Study Cohort 1: Proportion of participants with no abdominal pain by Numerical Rating Scale (NRS).

The abdominal pain NRS is a tool to rate the severity of abdominal pain over the past 24 hours using a score of 0 ("no pain") to 10 ("worst possible pain").

Time frame: Week 40

Pivotal Maintenance Sub-Study Cohort 1: Change from baseline in Inflammatory Bowel Disease Questionnaire (IBDQ) total score

IBDQ is a tool to the quality of life of individuals suffering from IBD. The total score ranges from 32 to 224, with higher scores correlating to a better quality of life.

Time frame: Week 40

Pivotal Maintenance Sub-Study Cohort 1: Incidence of UC-related hospitalizations.

Time frame: Week 0 through Week 40

Pivotal Maintenance Sub-Study Cohort 1: Proportion of participants with symptomatic (stool-frequency sub score [SFS] and = rectal bleeding sub score [RBS]) remission.

Symptomatic response is defined as ≥30% decrease from baseline in the composite clinical endpoint of the sum of SFS and RBS.

Time frame: Week 40

Pivotal Maintenance Sub-Study Cohort 1: Proportion of participants achieving clinical remission and no steroid use from the baseline to the time of endpoint analysis.

Time frame: Week 40

Pivotal Maintenance Sub-Study Cohort 1: Incidence of Treatment-Emergent Adverse Events (TEAEs), TEAEs of Special Interest, Treatment-Emergent Serious Adverse Events (TESAEs), and TEAEs leading to permanent study intervention discontinuation.

Time frame: Week 0 through 45 days after last dose

Pivotal Maintenance Sub-Study Cohort 1: Serum concentration of duvakitug measured over time.

Time frame: Week 0 through Week 40

Pivotal Maintenance Sub-Study Cohort 1: Incidence of treatment-emergent Anti-Drug Antibodies (ADA) against duvakitug.

Time frame: Week 0 through Week 40

Open-Label Extension Sub-Study: Incidence of Treatment-Emergent Adverse Events (TEAEs), TEAEs of Special Interest, Treatment-Emergent Serious Adverse Events (TESAEs), and TEAEs leading to permanent study intervention discontinuation.

Time frame: Week 40 of pivotal maintenance through 45 days after last dose