Clinical remission was defined as modified Mayo Score (mMS) of ≤ 2, including stool frequency subscore ≤ 1, rectal bleeding subscore=0, & endoscopy subscore ≤ 1 (score of 1 modified to exclude friability). MMS is a composite of 3 Mayo Score assessments, each scored on a scale from 0-3. The total score ranges from 0-9, with higher scores indicating more severe disease: stool frequency (0=Normal number of stools, 1=1-2 more stools than normal, 2=3-4 more stools than normal, 3=5 or more stools than normal); rectal bleeding (0=No blood seen or no bowel movement, 1=Stool with streaks of blood, 2=Stool with more than streaks of blood, 3=Blood alone passed); centrally read endoscopy (0=Normal appearance of mucosa, 1=Mild disease [erythema, decreased vascular pattern], 2=Moderate disease [marked erythema, absent vascular pattern, friability, erosions], 3=Severe disease [spontaneous bleeding, ulceration]). Percentages have been rounded off.

mITT included all participants who received at least one dose of study treatment and had at least one post-baseline efficacy measurement, with participants grouped according to their assigned treatment.

Clinical response was defined as decrease from baseline in mMS of ≥ 2 & ≥ 30% reduction from baseline and also decrease in rectal bleeding subscore of ≥ 1 or absolute rectal bleeding subscore of ≤ 1. MMS is a composite of 3 Mayo Score assessments, each scored on a scale from 0-3. The total score ranges from 0-9, with higher scores indicating more severe disease. Rectal bleeding scores are: 0=No blood seen or no bowel movement, 1=Stool with streaks of blood, 2=Stool with more than streaks of blood, 3=Blood alone passed. Percentages have been rounded off.

mITT included all participants who received at least one dose of study treatment and had at least one post-baseline efficacy measurement, with participants grouped according to their assigned treatment.

Endoscopic improvement was defined as a Mayo endoscopy subscore of ≤ 1 (score of 1 modified to exclude friability). Endoscopy scores were based on interpretation by a blinded central reader. The Mayo Score consists of participant-reported outcomes (stool frequency, rectal bleeding), endoscopy, and clinician-reported outcome (Physician's Global Assessment) components. The Mayo endoscopy sub-score ranges from 0 to 3 (0= No inflammation; 1= Mild inflammation [erythema, decreased vascular pattern]; 2=Moderate inflammation [marked erythema, absent vascular pattern, and friability]; 3= Severe inflammation [ulceration and spontaneous bleeding]), with higher scores indicating more severe disease. Percentages have been rounded off.

mITT included all participants who received at least one dose of study treatment and had at least one post-baseline efficacy measurement, with participants grouped according to their assigned treatment.

Endoscopic remission was defined as a Mayo endoscopy subscore of 0. Endoscopy scores were based on interpretation by a blinded central reader. The Mayo Score consists of participant-reported outcomes (stool frequency, rectal bleeding), endoscopy, and clinician-reported outcome (Physician's Global Assessment) components. The Mayo endoscopy sub-score ranges from 0 to 3 (0= No inflammation; 1= Mild inflammation [erythema, decreased vascular pattern and mild friability]; 2=Moderate inflammation [marked erythema, absent vascular pattern, and friability]; 3= Severe inflammation [ulceration and spontaneous bleeding]), with higher scores indicating more severe disease. Percentages have been rounded off.

mITT included all participants who received at least one dose of study treatment and had at least one post-baseline efficacy measurement, with participants grouped according to their assigned treatment.

An AE was defined as any untoward medical occurrence in a clinical investigation subject administered a pharmaceutical product, regardless of causal attribution. An AE can therefore be any of the following: Any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product; Any new disease or exacerbation of existing disease; Recurrence of an intermittent medical condition not present at baseline; Any deterioration in a laboratory value or other clinical test, associated with symptoms or leads to change in study treatment or concomitant treatment or discontinuation from study treatment; AEs related to a protocol-mandated intervention, including those that occur prior to assignment of study treatment.

Safety-evaluable population included all randomized participants who received at least one dose of study treatment, with participants grouped according to treatment received.

Pharmacokinetic (PK)-evaluable population included all participants with at least one post-dose serum PK sample in which vixarelimab concentration was evaluable. Overall number analyzed is the number of participants with data available for analysis. Number analyzed is the number of participants with data available for analysis at the specified timepoint.

Participants were considered to be ADA positive if they were ADA negative or had missing data at baseline but developed an ADA response following study drug exposure (treatment-induced ADA response), or if they were ADA positive at baseline and the titer of one or more post-baseline samples was at least 0.60 titer unit greater than the titer of the baseline sample (treatment-enhanced ADA response). The total number of participants who developed ADAs to vixarelimab was determined by summing the ADA-positive participants across all timepoints.

Safety-evaluable population included all randomized participants who received at least one dose of study treatment, with participants grouped according to treatment received. Overall number analyzed is the number of participants with data available for analysis. Number analyzed is the number of participants with data available for analysis at the specified timepoint.