12-Week Study of Plecanatide for CIC (The CIC3 Study)

Inclusion Criteria: * Male or female aged 18-80, inclusive * Meets modified Rome III criteria for functional chronic idiopathic constipation for at least 3 months with symptom onset for at least 6 months * Completed a colonoscopy in accordance with AGA colon cancer screening guidelines (5 years), with no clinically significant findings * Willing to maintain a stable diet during the study Exclusion Criteria: * Loose stool (mushy) or watery (Bristol score 6 or 7) stool in the absence of any laxative or prohibited medicine for \> 25% of BMs during the 3 months prior to screening visit OR during the 14 day pre-treatment assessment * Active peptic ulcer disease, diabetes or hypertension not adequately treated or not stable * History of cathartic colon, laxative, enema abuse, or ischemic colitis * Fecal impaction within 3 months of screening * Patient has had /has any: diseases or conditions associated with constipation (GI or CNS), structural abnormality of the GI tract or gastric bypass surgery, pelvic floor dysfunction, pseudo-obstruction, active infectious gastritis, diverticulitis, anal fissures or any disease or condition that can affect GI motility or defecation or can be associated with abdominal pain * Unexplained and clinically significant "alarm symptoms" including lower GI bleeding, iron-deficiency anemia, weight loss or systemic signs of infection or colitis * Major surgery, stroke or MI within 60 days of screening * Participated in a previous plecanatide clinical t…