Early data from a Phase 1b clinical trial show that the investigational therapy TD-1473 for patients with ulcerative colitis (UC) has demonstrated targeted action and effectiveness, according to the therapy’s developer and study sponsor, Theravance Biopharma. Preliminary data are from four weeks of treatment. The ongoing study (NCT02818686), which currently is recruiting participants, is for patients with moderate to severe active UC. TD-1473 is an orally administered, highly specific inhibitor of the Janus kinase (JAK) family of enzymes, which plays a key role in inflammation. Most importantly, TD-1473’s activity is restricted to the intestinal tract, which prevents the risk of systemic exposure and unwanted side effects. The study was designed to evaluate the treatment’s safety, tolerability, and pharmacokinetics (a therapy’s behavior in the body) in UC patients during a 28-day period. Additional endpoints include assessing TD-1473’s biologic effects by analyzing disease biomarkers and performing a thorough evaluation of clinical and endoscopic parameters. In the exploratory study, 10 patients from the first cohort received 80 mg of TD-1473 once a day for 28 days, while a control group of three patients received a placebo. Preliminary results from the first cohort revealed that TD-1473 induced a localized response (restricted to the intestine) with minimal systemic exposure. These results are similar to those observed in a Phase 1 study with healthy volunteers. Treatment with TD-1473 was not associated with impairment to patients’ immune systems (immunosuppression), as they showed no differences in infections and the number of several key immune cells including leukocytes, neutrophils, and lymphocytes compared with placebo controls.