Sponsor: Celgene International II Sàrl Induction and Maintenance Therapy of RPC1063 in UC 26 Jul 2019, Version 7.1 histopathology report (note: endoscopy and histopathology may be performed at Screening if no prior report is readily available) 3. Evidence of UC extending ≥ 15 cm from the anal verge as determined by Baseline endoscopy (flexible sigmoidoscopy or colonoscopy) 4. Have active UC defined as a complete Mayo score of 6 to 12 inclusive, with endoscopic subscore of ≥ 2, a rectal bleeding score of ≥ 1, and a stool frequency score ≥ 1 5. Must be currently receiving treatment with at least 1 of the following therapies and must continue on these therapies during Induction: Oral aminosalicylates at a therapeutic dose for their disease (eg, mesalamine, sulfasalazine, olsalazine, balsalazide), with the dose stable for at least 3 weeks prior to Screening endoscopy Prednisone (doses ≤ 20 mg per day) or equivalent receiving a stable dose for at least 2 weeks prior to Screening endoscopy Budesonide MMX therapy receiving a stable dose for at least 2 weeks prior to Screening endoscopy 6. Have undergone colonoscopy (or are willing to undergo colonoscopy during Screening): within the past 2 years, to screen for dysplasia (unless otherwise recommended by local and national guidelines) if the patient has had left-sided colitis of > 12 years duration or total/extensive colitis of > 8 years duration within the past 5 years, to screen for polyps if the patient age is > 45 years If oral aminosalicylates or corticosteroids have been recently discontinued, they must have been stopped for at least 2 weeks prior to the endoscopy used for Baseline Mayo score 7. Females of childbearing potential (FCBP): Must agree to practice a highly effective method of contraception throughout the trial until completion of the 90-day Safety Follow-up Visit. Highly effective methods of contraception are those that alone or in combination result in a failure rate of a Pearl index of less than 1% per year when used consistently and correctly. Acceptable methods of birth control in the trial are the following: combined hormonal (oestrogen and progestogen containing) contraception, which may be oral, intravaginal, or transdermal progestogen-only hormonal contraception associated with inhibition of ovulation, which may be oral, injectable, or implantable placement of an intrauterine device (IUD) placement of an intrauterine hormone-releasing system (IUS) bilateral tubal occlusion vasectomized partner complete sexual abstinence Periodic abstinence (calendar, symptothermal, post-ovulation methods), withdrawal (coitus interruptus), spermicides only, and lactational amenorrhoea method are not acceptable methods of contraception. 8. Must provide written informed consent/assent and have the ability to be compliant with the schedule of protocol assessments. The parent/legal guardian of the adolescent must sign an informed consent form. In addition, adolescent patients must also agree to participate in the study by signing an assent. 9. Patients must have documentation of positive Varicella zoster virus (VZV) immunoglobulin G (IgG) antibody status or complete VZV vaccination at least 30 days prior to randomization Exclusion Criteria: Patients are not eligible for this trial if they fulfill any of the following: Exclusions Related to General Health: 1. Have severe extensive colitis as evidenced by: Confidential 7 EDMS Doc. Number: 23968946 - 23968295 Sponsor: Celgene International II Sàrl Induction and Maintenance Therapy of RPC1063 in UC 26 Jul 2019, Version 7.1 12.1.8. Monitoring of Adverse Events and Serious Adverse Events ................. 75 12.1.10. Guidelines for Monitoring Patients Taking Their First Dose of RPC1063 ............................................................................................. 75 12.1.11. Clinical Laboratory Evaluations ........................................................... 76 12.2. Adverse Events and Serious Adverse Events........................................ 79 12.2.1. Definition of Adverse Events............................................................... 79 12.2.2. Definition of Serious Adverse Events................................................... 79 12.2.3. Assessment of Adverse Event Severity ................................................ 80 12.2.4. Assessment of Adverse Event Relationship to Investigational Drug ..... 80 12.2.5. Reporting of Serious Adverse Events................................................... 81 12.2.5.1. Reporting of Serious Adverse Events to Regulatory Authorities and Investigators ........................................................................................ 82 12.2.6. Adverse Events of Special Interest ....................................................... 82 12.2.7. Monitoring of Patients with Adverse Events, Serious Adverse Events, and Adverse Events of Special Interest................................................. 84 12.2.8. Treatment of Overdose of Investigational Drug.................................... 84 12.2.9. Procedures in Case of Pregnancy ......................................................... 84 12.2.10. Data Safety Monitoring Board ............................................................. 85 12.4. Appropriateness of Measurements ....................................................... 86 13. PLANNED STATISTICAL METHODS ............................................. 87 13.1. Determination of Sample Size.............................................................. 87 13.2. Statistical Methods............................................................................... 89 13.2.1. General Considerations........................................................................ 89 13.2.2. Analysis Populations............................................................................ 89 13.3. Disposition, Demographics and Baseline Characteristics...................... 90 13.4. Efficacy ............................................................................................... 90 13.4.1. Induction Period (Adult Patients) ......................................................... 90 13.4.1.1. Induction Period Primary Efficacy Analysis (Adult Patients) ............... 91 13.4.1.2. Induction Period Secondary Efficacy Analysis (Adult Patients) ........... 91 Confidential 20 EDMS Doc. Number: 23968946 - 23968295 Sponsor: Celgene International II Sàrl Induction and Maintenance Therapy of RPC1063 in UC 26 Jul 2019, Version 7.1 13.4.2. Maintenance Period (Adult Patients).................................................... 92 13.4.2.1. Maintenance Period Primary Efficacy Analysis.................................... 92 13.4.2.4. Handling Missing Data ........................................................................ 93 13.6. Interim Analyses.................................................................................. 94 13.7. Induction Period Analysis .................................................................... 95 13.8. End of Study Analysis.......................................................................... 95 13.9. Treatment Failure Rules....................................................................... 95 14. DIRECT ACCESS TO SOURCE DATA/DOCUMENTS.................... 96 14.1. Monitoring........................................................................................... 96 14.2. Data Management/Coding.................................................................... 96 14.3. Quality Assurance and Inspections....................................................... 97 15. QUALITY CONTROL AND QUALITY ASSURANCE..................... 98 15.1. Study Monitoring and Source Data Verification................................... 98 15.2. Product Quality Complaint................................................................... 98 16. ETHICS............................................................................................... 99 16.1. Institutional Review Board or Independent Ethics Committee.............. 99 16.2. Ethical Conduct of the Trial ................................................................. 99 16.3. Patient Information and Informed Consent/Assent ............................... 99 16.4. Patient Data Protection....................................................................... 100 16.5. Investigator Obligations..................................................................... 100 16.6. Protocol Signatures............................................................................ 100 17. DATA HANDLING AND RECORD KEEPING............................... 101 17.1. Inspection of Records ........................................................................ 101 17.2. Retention of Records.......................................................................... 101 18. PUBLICATION POLICY, FINANCING, AND INSURANCE ......... 102 Confidential 21 EDMS Doc. Number: 23968946 - 23968295 Sponsor: Celgene International II Sàrl Induction and Maintenance Therapy of RPC1063 in UC 26 Jul 2019, Version 7.1 Appendix 2: Investigator Responsibilities............................................................ 109 Appendix 3: BENEFIT RISK ASSESSMENT...................................................... 110 Confidential 22 EDMS Doc. Number: 23968946 - 23968295 Sponsor: Celgene International II Sàrl Induction and Maintenance Therapy of RPC1063 in UC 26 Jul 2019, Version 7.1 List of Tables Table 1: Schedule of Events............................................................................... 42 Table 2: Cardiac