Inclusion Criteria:  Male and female subjects ≥ 18 and ≤ 75 years of age at baseline. Capable of giving informed consent and complying with study procedures. Normal renal function or mild renal impairment as determined by the Investigator following review of clinical laboratory test results. Laboratory and medical history parameters within the protocol-defined ranges. Diagnosis of UC for 90 days or greater prior to baseline, confirmed by colonoscopy during the screening period, with exclusion of current infection, colonic dysplasia, and/or malignancy. Appropriate documentation of biopsy results consistent with the diagnosis of UC, in the assessment of the Investigator, must be available. Active UC with a full Mayo score of 6 to 12 points and endoscopic subscore of 2 or higher confirmed by central reader. Subject must have received COVID-19 vaccine >2 months before first dose of study drug.  Exclusion Criteria:  Pregnant or nursing women. Clinically significant history of cardiovascular, hematologic, renal, hepatic, bronchopulmonary, immunologic, lipid metabolism disorders, or drug hypersensitivity as determined by the Investigator. Current and/or recent history of a clinically significant infection. Any history of malignancies, except for non-melanoma skin cancers (unless it is metastatic). Positive blood screen for human immunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg), or hepatitis C antibody. Any condition or finding that in the Investigator's opinion would put the subjects or study conduct at risk if the subjects were to participate in the study. Current diagnosis of Crohn's disease (CD) or diagnosis of indeterminate colitis (IC). Current diagnosis of fulminant colitis and/or toxic megacolon, or active Clostridium difficile colitis. Subject with disease limited to the rectum (ulcerative proctitis) during the screening endoscopy. Subject with previous exposure to JAK inhibitor (eg, tofacitinib, baricitinib, filgotinib, upadacitinib).