Comaprison of Efficacy and Safety Between Etrasimod vs Mesalazine in Chinese Adults With Active UC

Living with ulcerative colitis (UC) can be very difficult. This chronic gut condition causes repeated bouts of diarrhoea, rectal bleeding, abdominal pain, and extreme tiredness. It often strikes young adults in their 20s and 40s, and it can disrupt work, relationships, and daily life. Over time, persistent inflammation also raises the risk of colon cancer. Currently, the standard first treatment for mild-to-moderate UC in China is mesalazine (5-ASA), an oral anti-inflammatory drug. While it helps many people, a large number of patients either do not respond well enough, relapse frequently, or cannot tolerate its side effects, such as kidney problems. Stronger drugs like biologics or JAK inhibitors are usually held back until after mesalazine fails. This step-up approach may delay effective disease control and allow gut damage to progress. Etrasimod is a new type of oral pill that works differently. It gently steers certain immune cells away from the gut by blocking their exit from lymph nodes-like keeping "firefighters" away from the "fire" inside the colon. Because it is taken just once a day and does not require injections, it could be more convenient for long-term use. Global clinical trials have shown that etrasimod helps more patients achieve remission than a placebo, but no large study has directly compared it with mesalazine in Chinese adults. This study aims to fill that gap. The study will recruit about 320 adults with active UC from multiple hospitals across China. Both individuals who are newly diagnosed (within the last month) and those who have used conventional drugs like mesalazine, steroids, or immune suppressors without enough improvement may join-as long as such individuals have never taken biologics or other small-molecule therapies. Participants will be randomly assigned to one of two groups: one group takes etrasimod 2 mg once daily, and the other takes mesalazine at standard doses. The treatment lasts for 24 weeks. The core research question focuses on whether etrasimod leads to more patients achieving clinical remission-meaning no rectal bleeding, nearly normal bowel habits, and visible healing of the colon lining seen on a camera test (endoscopy)-compared with mesalazine at 24 weeks. The study will also evaluate many other real-world benefits, such as improvement in daily symptoms, deeper tissue healing (examined under a microscope), normalisation of blood and stool inflammation markers, and better scores on quality-of-life questionnaires that assess mood, work, and social activities. Since this is an open-label study, both patients and attending clinical staff will know which drug is being taken, but the clinical staff who review the endoscopic images and biopsy samples will not know the treatment assignments to ensure objective study results. Safety is a top priority for the study. All participants will receive close monitoring for side effects, with regular blood tests, heart checks, and eye examinations conducted as needed. All unwanted events occurring during the 24-week treatment period and the subsequent 4-week follow-up period will be recorded. The study team may terminate the trial early if serious safety concerns arise. By generating direct head-to-head evidence in a Chinese population, this research will support clinical staff and patients to make better-informed treatment choices. If etrasimod proves to be more effective and equally safe, it could offer a new, convenient, and early intervention treatment option that optimises UC management strategies in China-potentially enabling more patients to achieve early disease control and maintain long-term gut health. Study participation is completely voluntary, and participant withdrawal may occur at any time without impact on routine medical care. All personal data collected during the study will be strictly confidential.