Phase III Study to Evaluate the Efficacy and Safety 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: * Patient with history of surgical resection of stomach, gallbladder, small intestine, or large intestine (excluding resection of appendicitis and benign polyp) * Patient with history or current affection of inflammatory bowel disease (Crohn's disease or ulcerative colitis) * Patient with history or current affection of ischemic colitis * Patient currently affected by infectious enteritis * Patient currently affected by hyperthyroidism or hypothyroidism * Patient currently affected by active peptic ulcer * In the case of a female patient, the one currently affected by endometriosis or uterine adenomyosis * Patient with high depression or anxiety considered to influence drug evaluation * Patient with history of abuse of drug or alcohol within a year before consent acquisition, or with current abuse * Patient who used or underwent or will use or undergo drug/therapy/test prohibited to combine 3 days before the start of bowel habit observation period (Day -17) or thereafter * Patient with history or current affection of malignant tumor * Patient currently affected by serious cardiovascular disease, respiratory disease, kidney disease, hepatic disease, gastrointestinal disease (excluding IBS), hemorrhagic disease, or neural/mental disease * Patient with history of drug allergy