In three phase 3 trials involving patients with ulcerative colitis, tofacitinib (an oral, small-molecule Janus kinase inhibitor) was more effective as induction and maintenance therapy than placebo. Infections were more common with tofacitinib. Ulcerative colitis is characterized by an increased frequency of bowel movements and bloody diarrhea, which has a negative effect on quality of life. 1 Current therapies for ulcerative colitis include mesalamine, glucocorticoids, thiopurines, and antagonists to tumor necrosis factor (TNF) and α4β7 integrin. 1 – 5 Many patients do not have a response to these therapies or have a response that is not sustained. Additional treatment options with new mechanisms of action are needed to increase efficacy rates. The Janus kinase (JAK) family comprises four intracellular tyrosine kinases — JAK1, JAK2, JAK3, and nonreceptor tyrosine-protein kinase 2 — that activate signal transducers and . . .