This study is for adults with Irritable Bowel Syndrome with Diarrhea (IBS-D), a condition causing stomach pain and diarrhea. The research tests a medicine called CIN-103 to see if it helps and is safe. Participants will have a screening visit, a baseline visit, five visits during 12 weeks of treatment, and one follow-up visit. They'll take the study medicine twice a day and fill out daily diaries about their symptoms. Researchers will compare different doses of CIN-103 to a placebo, which is a pill with no medicine, to check how well it works.

**Key points to consider:**

• The study lasts about 15 weeks with 8 visits in total.
• Participants will take medicine twice daily and keep a daily diary.
• Ensure eligibility by meeting certain health criteria.