Study to Evaluate the Efficacy and Safety of Vibegron Administered Orally for 12 Weeks to Women With Irritable Bowel Syndrome

Inclusion Criteria: * Diagnosis of irritable bowel syndrome (IBS) with predominantly diarrhea (IBS-D) or IBS with mixed episodes of diarrhea and constipation (IBS-M) according to the Rome IV criteria * Has completed a colonoscopy according to the American Gastroenterological Association criteria, with no clinically significant findings in the last 5 years * Has no clinically significant findings on a physical examination or clinical laboratory tests that could interfere with study participation or confound study assessments, in the opinion of the Investigator. Serum tissue transglutaminase antibody (IgA) must be negative. Fecal calprotectin testing is optional and should only be considered if there is a strong suspicion that the participant has inflammatory bowel disease (IBD) (eg, family history in a 1st degree relative, other genetic factors, etc.) or other organic disease, according to the clinical judgement of the investigator. Exclusion Criteria: * Diagnosis of IBS-C or IBS-U per Rome IV criteria * History of chronic idiopathic constipation or functional constipation * Structural abnormality of the gastrointestinal tract or a disease (e.g., known small intestine bacterial overgrowth) or condition that can affect gastrointestinal motility * History of a gastrointestinal motility disorder other than IBS (e.g., gastroparesis, intestinal pseudo-obstruction, achalasia, Parkinsons disease, multiple sclerosis, spinal cord injury) * Prior history of a gastrointestinal malignancy, inflammatory bowel disease, celiac disease * Planned gastrointestinal or abdominal surgery within the next 6 months * Co-existing gastroesophageal reflux disease or functional dyspepsia with symptoms predominant to IBS symptoms * Symptoms or diagnosis of a medical condition other than IBS that may contribute to abdominal pain (e.g., interstitial cystitis; fibromyalgia currently being treated with pregabalin or gabapentin; and endometriosis with uncontrolled abdominal pain)