A Study to Evaluate the Effect of ASP0456 in Patients With Constipation Predominant Irritable Bowel Syndrome

Inclusion Criteria: * Patients who had abdominal pain or discomfort repeatedly for at least 3 days per month during the 3 months before screening examination associated with at least 2 out of the following 3 conditions: (1) Improvement with defecation; (2) Onset associated with a change in frequency of stool; and (3) Onset associated with a change in form (appearance) of stool, and had the above symptom (IBS symptom) 6 months or more before the screening examination period. * Patients with ≥25% of stools hard or lumpy (with each bowel movement occurring without antidiarrheal, laxative, suppository or enema) and \<25% of them loose (mushy) or watery during the 3 months before the screening examination. * Patients who had pancolonoscopy or contrast enema (or sigmoidoscopy) after the onset of IBS symptom and had no organic changes. Exclusion Criteria: * Patients with a history of surgical resection of the stomach, gallbladder, small intestine or large intestine * Patients with other concurrent diseases that may affect the digestive tract passage or large intestinal function * Patients with other concurrent diseases that may affect the assessment of abdominal pain/discomfort * Patients with blood pressure, pulse rate, clinical laboratory test, or 12-lead ECG at the time of screening examination that was rated as Grade 2 or greater on the "Severity Criteria for Drug Adverse Reaction" and judged to be clinically significant