An Efficacy and Safety Study of Ontamalimab as Maintenance Therapy in Participants With Moderate to Severe Ulcerative Colitis

Inclusion Criteria:

• Participants and/or their parent or legally authorized representative must have anunderstanding, ability, and willingness to fully comply with study procedures andrestrictions.

• Participants must be able to voluntarily provide written, signed, and dated (personally or via a legally authorized representative) informed consent and/orassent, as applicable, to participate in the study.

• Participants must have completed the 12-week induction treatment period (SHP647-301 [NCT03259334] and SHP647-302 [NCT03259308]).

• Participants must have achieved clinical response in induction study (SHP647-301 [NCT03259334] and SHP647-302 [NCT03259308]). Clinical response is defined as: i) A decrease from the induction study (SHP647-301 [NCT03259334] and SHP647-302 [NCT03259308]) baseline in the composite score of patient reported symptoms usingdaily e-diary and centrally read endoscopy of at least 2 points and at least 30percent (%), with an accompanying decrease in the sub score for rectal bleedinggreater than or equal to (>=) 1 point or a sub score for rectal bleeding less than orequal to (<=) 1 OR ii) A decrease from the induction study (SHP647-301 [NCT03259334]and SHP647-302 [NCT03259308]) baseline in total Mayo score of at least 3 points and atleast 30%, with an accompanying decrease in the rectal bleeding sub score of at least 1 point or an absolute rectal bleeding sub score of 0 or 1. For eligibility assessment, clinical response will be determined based on the centrallyread endoscopy performed during screening and at Week 12 of induction study (SHP647-301 [NCT03259334] and SHP647-302 [NCT03259308]).

• Participants receiving any treatment(s) for ulcerative colitis (UC) are eligible providedthey have been, and are anticipated to be, on a stable dose for the designated period oftime.

Exclusion Criteria:

• Participants who had major protocol deviation(s) (as determined by the sponsor) ininduction study (SHP647-301 [NCT03259334] and SHP647-302 [NCT03259308]).
• Participants who permanently discontinued investigational product because of anadverse event (AE), regardless of relatedness to investigational product, in inductionstudy (SHP647-301 [NCT03259334] and SHP647-302 [NCT03259308]).
• Participants who are likely to require surgery for UC during the study period.
• Participants are females who became pregnant during induction study (SHP647-301 [NCT03259334] and SHP647-302 [NCT03259308]), females who are planning to becomepregnant during the study period, or males or females of childbearing potential notagreeing to continue using appropriate contraception methods (that is [i.e,] highlyeffective methods for female and medically appropriate methods for male studyparticipants) through the conclusion of study participation.
• Participants who do not agree to postpone donation of any organ or tissue, includingmale participants who are planning to bank or donate sperm and female participants whoare planning to harvest or donate eggs, for the duration of the study and through 16weeks after last dose of investigational product.
• Participants who, in the opinion of the investigator or the sponsor, will beuncooperative or unable to comply with study procedures.
• Participants who have a newly diagnosed malignancy or recurrence of malignancy (otherthan resected cutaneous basal cell carcinoma, squamous cell carcinoma, or carcinoma insitu of the uterine cervix that has been treated with no evidence of recurrence).
• Participants who have developed any major illness/condition or evidence of an unstableclinical condition (example [eg], renal, hepatic, hematologic, gastrointestinal (except disease under study), endocrine, cardiovascular, pulmonary, immunologic [eg,Felty's syndrome], or local active infection/infectious illness) that, in theinvestigator's judgment, will substantially increase the risk to the participant if heor she participates in the study.
• Participants with any other severe acute or chronic medical or psychiatric conditionor laboratory or electrocardiogram (ECG) abnormality that may increase the riskassociated with study participation or investigational product administration or mayinterfere with the interpretation of study results and, in the judgment of theinvestigator, would make the participant inappropriate for entry into this study.
• Participants with known exposure to Mycobacterium tuberculosis (TB) since testing atscreening in induction study (SHP647-301 [NCT03259334] and SHP647-302 [NCT03259308])and who are without a generally accepted course of treatment.
• Participants who are investigational site staff members or relatives of those sitestaff members or participants who are sponsor employees directly involved in theconduct of the study.
• Participants who are participating in or plan to participate in other investigationalstudies (other than induction study SHP647- 301 [NCT03259334] and SHP647-302 [NCT03259308]) during study SHP647-303 [NCT03290781].