Primary Outcomes Measures: Induction Study 1: Percentage of Participants With Clinical Response at Week I-12, Clinical response was defined as a decrease from induction baseline in the modified Mayo score by greater than or equal to (\>=) 30 percent (%) and \>=2 points, with either a \>=1 point decrease from baseline (Week 0 of IS-1) in the rectal bleeding subscore or a rectal bleeding subscore of 0 or 1. The modified Mayo scores consisted of 3 subscores: stool frequency, rectal bleeding and endoscopic subscore, each subscore graded from 0 (normal) to 3 (severe) with higher scores indicating more severe disease. These individual subscores were summed up to give a total modified Mayo score range of 0 (normal) to 9 (severe disease), where higher scores indicated more severe disease activity. This outcome measure was planned to be analyzed for specified arms only., At Week I-12|Induction Study 2: Percentage of Participants With Clinical Remission at Week I-12, Clinical remission was based on the modified Mayo score. Clinical remission was defined as Mayo stool frequency subscore of 0 or 1 and not increased from baseline (Week 0 of IS-2), a Mayo rectal bleeding subscore of 0, and Mayo endoscopic subscore of 0 or 1 with no friability. The modified Mayo scores consisted of 3 subscores: stool frequency, rectal bleeding and endoscopic subscore, each subscore graded from 0 (normal) to 3 (severe) with higher scores indicating more severe disease. These individual subscores were summed up to give a total modified Mayo score range of 0 (normal) to 9 (severe disease), where higher scores indicated more severe disease activity. This outcome measure was planned to be analyzed for specified arms only., At Week I-12|Maintenance Study: Percentage of Participants With Clinical Remission at Week M-44, Clinical remission was based on the modified Mayo score. Clinical remission was defined as Mayo stool frequency subscore of 0 or 1 and not increased from baseline (Week 0 of IS-1 and IS-2), a Mayo rectal bleeding subscore of 0, and Mayo endoscopic subscore of 0 or 1 with no friability. The modified Mayo scores consisted of 3 subscores: stool frequency, rectal bleeding and endoscopic subscore, each subscore graded from 0 (normal) to 3 (severe) with higher scores indicating more severe disease. These individual subscores were summed up to give a total modified Mayo score range of 0 (normal) to 9 (severe disease), where higher scores indicated more severe disease activity. This outcome measure was planned to be analyzed for randomized arms only., At Week M-44, The trials look to find new ways to prevent, detect, or treat disease and improve quality of life. What are clinical trials for ulcerative colitis? Clinical trials—and other types of clinical studies—are part of medical research and involve people like you. When you volunteer to take part in a clinical study, you help doctors and , An Extension Study for Treatment of Moderately to Severely Active Ulcerative Colitis. Study Details | Source. Sponsor: Pfizer; The purpose of this open-label extension (OLE) study is to evaluate the safety and efficacy of etrasimod in participants with moderately to severely active ulcerative colitis (UC) who previously received double-blind treatment (either etrasimod 2 mg per day or placebo .