Study to Evaluate the Safety, Efficacy, and Pharmacokinetics of Budesonide Extended-release Tablets in Pediatric Subjects Aged 5 to 17 Years With Active, Mild to Moderate Ulcerative Colitis

Inclusion Criteria: * Established diagnosis of UC is based on: * Clinical history * Characteristic endoscopic findings * Histopathology results from biopsies * Age 5 to 17 years, inclusive, at Screening. Subjects should weigh greater than 13.6 kg at Baseline. * Active UC of mild or moderate severity, defined as a total Mayo score between 4 and 10, inclusive, with rectal bleeding subscore of ≥ 1, stool frequency subscore of ≥1 and an endoscopy subscore of ≥ 1. * If on a background oral or rectal 5-ASA, the dose and formulation have remained unchanged for at least 6 weeks prior to Visit 2 (randomization), Baseline and the subject is willing to remain on the same formulation and dose for the duration of the study. Exclusion Criteria: 1. Current or prior diagnosis of Crohn's disease or indeterminate colitis. 2. Limited distal proctitis (disease involving only the first 15 centimeters or less proximal to the anal verge. 3. Severe UC, defined as total Mayo score \>10. 4. Not currently in an active phase or flare, defined as a total Mayo score \<4, or Mayo score between 4 and 10, but Mayo subscore of 0 for rectal bleeding, stool frequency or endoscopy. 5. Infectious colitis (based on positive microbiologic tests at Screening) or any recent history of infectious colitis (within 30 days prior to Screening). 6. Prior gastrointestinal surgery, except appendectomy or hernia (e.g., inguinal, umbilical). NOTE: Prior cholecystectomy is not exclusionary if more than 1 year prior to Screening. 7. Evidence or history of toxic megacolon or bowel resection.