This clinical trial is focused on studying a condition known as ulcerative colitis, specifically targeting patients with mild to moderate left-sided ulcerative colitis. Ulcerative colitis is a chronic disease that causes inflammation and sores in the lining of the large intestine, which includes the colon and rectum. The study will test a new treatment called Rifamycin 1% in situ gelling solution, which is administered rectally. This treatment is being compared to a matching placebo to see if it can help patients achieve remission, meaning a reduction or disappearance of symptoms.

The purpose of the study is to evaluate the effectiveness and safety of this new treatment. Participants will receive the treatment or placebo for a period of six weeks. During this time, the study will monitor the proportion of patients who achieve clinical remission, which is defined by a specific scoring system that measures stool frequency, rectal bleeding, and endoscopic findings. The study will also look at other outcomes, such as partial remission, clinical response, and endoscopic improvement, which involves checking the inside of the colon with a camera to see if there is less inflammation.

Throughout the study, the safety of the treatment will be closely monitored by comparing the number of adverse reactions between the treatment and placebo groups. The trial aims to provide valuable information on whether this new treatment can effectively manage symptoms of ulcerative colitis and improve the quality of life for those affected by this condition.