A Study of Guselkumab in Participants With Moderately to Severely Active Ulcerative Colitis

This study is open to adults aged 18 and older who have a clear diagnosis of moderate to severe ulcerative colitis. To qualify, you must have tried standard medical therapies that either did not control your symptoms well enough or caused side effects that meant you had to stop taking them. You will also need to have routine health tests, such as blood checks, to ensure taking part is safe for you.

You cannot join this study if your inflammation is only in the rectum or affects less than 20 centimetres of your bowel. It is also not suitable for people with other types of bowel inflammation, such as Crohn's disease, or anyone who currently has a stoma bag or an abnormal tunnel in the bowel wall known as a fistula. Certain medications are also not allowed during the trial.

If you take part, you will first have a screening period to check your overall health and confirm that the study is safe for you. This will include blood tests, stool samples, and an examination of your bowel lining. During the trial, you will be randomly assigned to receive either guselkumab or a dummy treatment (placebo). You will need to attend hospital clinic visits for health checks, symptom reviews, and study medication doses, which may be given through a drip into a vein or as an injection under the skin. You will also be asked to keep a simple diary tracking your bowel habits. The trial typically lasts for several months up to a year, followed by a safety check-up once treatment ends.