Identification of Biomarkers of Janus Kinase Inhibitor Therapy in Patients With Ulcerative Colitis

This study aims to provide new mechanistic insights into the molecular determinants of response or nonresponse to Janus Kinase inhibitor therapy and the biological heterogeneity that exists in Ulcerative Colitis. This study will include patients who are initiating Janus Kinase inhibitor therapy according to standard of care. This study consists of: * Part 1: 8 or 10 week induction therapy followed by an 8-week maintenance therapy * Part 2: Patients who continue Janus Kinas inhibitor therapy after part 1 will be followed further for a total of 2 years, or until discontinuation of Janus Kinase inhibitor therapy (whichever is first)