A Study to Learn About the Safety, Effects and Pharmacokinetics of Study Medication (PF-07054894) for the Treatment of Ulcerative Colitis

Inclusion Criteria: * Confirmed diagnosis of moderate to severe (Part A) or mild to moderate (Part B) UC for ≥3 months prior to baseline. * Active disease beyond the rectum (\>15 cm of active disease from the anal verge at the screening endoscopy). Part A (moderate to severe): Must have a 5 to 9 score on the modified mayo score, including an endoscopy subscore of at least 2. Part B (mild to moderate): Participants with mMS of 4 to 6, ES of ≥2 and RB score of ≥1 * Must have inadequate response to, loss of response to, or intolerance to at least one conventional therapy for UC. * Total body weight \>40 kg (88.2 lb). Exclusion Criteria: * Presence of indeterminate; microscopic; ischemic; infectious; radiation colitis; diverticular disease; Crohn's disease; colonic stricture; colonic obstruction/ resection; presence of cancer. * History of bowel surgery within 6 months prior to baseline. * History of significant trauma or major surgery within 4 weeks of screening or considered in imminent need of surgery or with elective surgery scheduled to occur during the study. * Presence of clinical signs of fulminant colitis or toxic megacolon, primary sclerosing cholangitis and evidence of colonic dysplasia, adenomas or neoplasia. * Clinically significant infections within 6 months of baseline