Adult participants with moderate to severe UC (Mayo score of 6 to 12 points with endoscopy subscore of 2 to 3 points), confirmed by colonoscopy with biopsy or by flexible sigmoidoscopy with biopsy, were enrolled at 80 sites worldwide. The study enrolled 576 participants, including 186 participants under the original protocol and protocol Amendments 1 and 2, and 390 participants under protocol Amendments 3 and 4.