Inclusion Criteria:

Participants must meet all of the following inclusion criteria to be eligible for enrollment into the study.

• Subjects and/or their parent or legally authorized representative must have an understanding, ability, and willingness to fully comply with study procedures and restrictions.
• Subjects must be able to voluntarily provide written, signed, and dated (personally or via a legally authorized representative) informed consent and/or assent, as applicable, to participate in the study.
• Subjects must have completed the 12-week induction treatment period from study.
• Subjects must have achieved clinical response in induction study SHP647-301 or SHP647-302. Clinical response is defined as:
  • A decrease from the induction study (SHP647-301 or SHP647-302) baseline in the composite score of patient-reported symptoms using daily e-diary and centrally read endoscopy of at least 2 points and at least 30%, with an accompanying decrease in the subscore for rectal bleeding ≥ 1 point or a subscore for rectal bleeding ≤ 1; OR
  • A decrease from the induction study (SHP647-301 or SHP647-302) baseline in total Mayo score of at least 3 points and at least 30%, with an accompanying decrease in the rectal bleeding subscore of at least 1 point or an absolute rectal bleeding subscore of 0 or 1.
• For eligibility assessment, clinical response will be determined based on the centrally read endoscopy performed during screening and at Week 12 of induction study SHP647-301 or SHP647-302.
• Subjects receiving any treatment(s) for UC are eligible provided they have been, and are anticipated to be, on a stable dose for the designated period of time.

Exclusion Criteria:

Participants are excluded from the study if any of the following exclusion criteria are met:

• Subjects who had major protocol deviation(s) (as determined by the sponsor) in induction study SHP647-301 or SHP647-302.
• Subjects who permanently discontinued investigational product because of an AE, regardless of relatedness to investigational product, in induction study SHP647-301 or SHP647-302.
• Subjects who are likely to require surgery for UC during the study period.
• Subjects are females who became pregnant during induction study SHP647-301 or SHP647-302, females who are planning to become pregnant during the study period, or males or females of childbearing potential not agreeing to continue acceptableusing appropriate contraception methods through the conclusion of study participation.
• Subjects who do not agree to postpone donation of any organ or tissue, including male subjects who are planning to bank or donate sperm and female subjects who are planning to harvest or donate eggs, for the duration of the study and through 16 weeks after last dose of investigational product.
• Subjects who, in the opinion of the investigator or the sponsor, will be uncooperative or unable to comply with study procedures.
• Subjects who have a newly diagnosed malignancy or recurrence of malignancy (other than resected cutaneous basal cell carcinoma, squamous cell carcinoma, or carcinoma in situ of the  uterine cervix that has been treated with no evidence of recurrence).
• Subjects who have developed any major illness/condition or evidence of an unstable clinical condition (e.g., renal, hepatic, hematologic, gastrointestinal (except disease under study), endocrine, cardiovascular, pulmonary, immunologic [e.g., Felty’s syndrome], or local active infection/infectious illness) that, in the investigator’s judgment, will substantially increase the risk to the subject if he or she participates in the study.
• Subjects with any other severe acute or chronic medical or psychiatric condition or laboratory or ECG abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the subject inappropriate for entry into this study.
• Subjects with known exposure to Mycobacterium tuberculosis (TB) since testing at screening in induction study SHP647-301 or SHP647-302 and who are without a generally accepted course of treatment.
• Subjects who are investigational site staff members or relatives of those site staff members or subjects who are sponsor employees directly involved in the conduct of the study.
• Subjects who are participating in or plan to participate in other investigational studies (other than induction study SHP647-301 or SHP647-302) during study SHP647-303.