This study is testing a new medicine, SAR442970, for adults with **Ulcerative Colitis** (UC), a disease that causes inflammation in the colon. This is a *phase 2b study*, which means it's looking at how well the medicine works and if it's safe. It's a *randomized* and *double-blind* study, so neither the participants nor the researchers know who is getting the medicine or a placebo. The study lasts up to 168 weeks, with 158 weeks of treatment. Some people may take part in an *open-label* period where they know they are getting the medicine for up to 104 weeks. Key Points: - Participants spend up to 168 weeks in the study, including potential long-term treatment. - **Eligibility**: Ages 18-75 with moderate to severe UC and prior treatment history. - Some exclusions: other bowel diseases, recent infections, or certain health conditions. This is not all the information about the study. If you're interested, you should contact the study team for more details.