Study to Assess Safety and Efficacy of Tenapanor for Treatment of IBS-C in Pediatric Patients 12 to Less Than 18 Years

Inclusion Criteria:

• ≥12 and <18 years old

• Patient weighs ≥18 kg at the time the patient provides written assent

• Females of child-bearing potential must have negative pregnancy test at Visit 1 (serum) and Visit 2 (urine) and confirm the use of appropriate contraception (including abstinence).

• Patient meets the Rome IV criteria for child/adolescent diagnosis of IBS-C

• Patient is willing to discontinue any laxatives used in favor of theprotocol-permitted rescue medicine (which will only be allowed after 72 hours withno bowel movement)

• Patient meets the entry criteria assessed during the 2-week Screening period.

• Ability of both the patient and parent/guardian/LAR to communicate with theInvestigator and to comply with the requirements of the entire study, including anunderstanding of the assessments in the eDiary and how to use the eDiary device

• Patient must provide written assent and the parent/guardian/LAR must provide writteninformed consent before the initiation of any study-specific procedures

Exclusion Criteria:

• Functional diarrhea as defined by Rome IV child/adolescent criteria

• IBS with diarrhea (IBS-D), mixed IBS (IBS-M), or unsubtyped IBS as defined by RomeIV child/adolescent criteria

• History of non-retentive fecal incontinence.

• Required manual disimpaction any time prior to randomization (after consent);

• Has both unexplained and clinically significant alarm symptoms (lowergastrointestinal [GI] bleeding [rectal bleeding or heme-positive stool],iron-deficiency anemia, or any unexplained anemia, or weight loss) and systemicsigns of infection or colitis, or any neoplastic process

• Patient has any of the following conditions:

• Celiac disease, or positive serological test for celiac disease

• Cystic fibrosis

• Hypothyroidism that is untreated or treated with thyroid hormone

• Down's syndrome or any other chromosomal disorder

• Active anal fissure

• Anatomic malformations (eg, imperforate anus)

• Intestinal nerve or muscle disorders (eg, Hirschprung disease)

• Neuropathic conditions (eg, spinal cord abnormalities)

• Lead toxicity, hypercalcemia

• Neurodevelopmental disabilities producing a cognitive delay that precludescomprehension and completion of the daily eDiary (Electronic handheld device)

• Inflammatory bowel disease

• Childhood functional abdominal pain syndrome

• Childhood functional abdominal pain;

• Poorly treated or poorly controlled psychiatric disorders that might influencehis or her ability to participate in the study;

• Lactose intolerance that is associated with abdominal pain or discomfort

• History of cancer other than treated basal cell carcinoma of the skin; (Note:Patients with a history of cancer are allowed provided that the malignancy hasbeen in a complete remission for at least 5 years before the RandomizationVisit.)

• History of diabetic neuropathy.

• Use of medications that are known to affect stool consistency (ProhibitedMedications), including fiber supplements, anti-diarrheals, cathartics, antacids,opiates, prokinetic drugs, laxatives, enemas, antibiotics during the Screeningperiod; unless specified as rescue medication, and used accordingly as directed bythe Investigator.

• Patient has had surgery that meets any of the following criteria:

• Bariatric surgery for treatment of obesity, or surgery to remove a segment ofthe GI tract at any time before the Screening Visit;

• Surgery of the abdomen, pelvis, or retroperitoneal structures during the 6months before the Screening Visit;

• An appendectomy or cholecystectomy during the 60 days before the ScreeningVisit;

• Other major surgery during the 30 days before the Screening Visit

• History of alcohol or substance abuse

• Participation in other clinical trials within 1 month prior to Screening

• Patient and/or parent/guardian/LAR is involved in the conduct and/or administrationof this trial as an investigator, sub-investigator, trial coordinator, or otherstaff member, or the patient is a first-degree family member, significant other, orrelative residing with one of the above persons involved in the trial

• If, in the opinion of the Investigator, the patient is unable or unwilling tofulfill the requirements of the protocol or has a condition, which would render theresults uninterpretable