OPPS-2071 for the treatment of IBS-D

INTERVENTION: placebo group:placebo;Medium‐dose drug group:OPS‐2071 100 mg/bid;High‐dose drug group:OPS‐2071 200 mg/bid;Low‐dose drug group:OPS‐2071 50 mg/bid; CONDITION: Irritable Bowel Syndrome with Diarrhea (IBS‐D) PRIMARY OUTCOME: Abdominal pain;Type of stool; SECONDARY OUTCOME: Changes in bowel movement frequency;Improvement in abdominal pain;Subjective relief in the subjects;Changes in the sense of urgency to defecate;Changes in the consistency of stool;Improvement in abnormal bowel movements;Gut microbiota;Changes in abdominal discomfort;Safety; INCLUSION CRITERIA: 1. Be able to fully understand and willing to comply with the trial process, voluntarily participate in this trial and sign the informed consent form; 2. Signed informed consent, age >= 18 and <=65 years old; 3. Subjects who met the Rome IV criteria for a diagnosis of IBS‐D; 4. The screening period should meet the following criteria: (1)The weekly average of the most severe abdominal pain intensity on the NRS scale is >=3.0; (2)Stool consistency classified as Bristol 6 or 7, and for at least =2 days per week; (3)Completion of diary card records for at least 10 days; (4)Taking emergency medication (pinaverium) continuously or intermittently for <=2 days. 5. Subjects who are able to maintain a stable lifestyle and dietary habits during the trial period, without making any new major changes that may affect IBS‐D symptoms (e.g., starting a new diet or changing usual lifestyle habits).