A Study to Assess Adverse Events and Change in Symptoms With Linaclotide Versus Placebo in Pediatric Subjects, Ages 2 to 5 Years, With Functional Constipation

Inclusion Criteria:

• Caregiver/parent/guardian/legally authorized representative (LAR) is willing andable to comply with procedures required in this protocol, prior to the initiation ofany screening or study-specific procedures. In addition, thecaregiver/parent/guardian/LAR who will be completing the electronic diary (eDiary)must be able to read and understand the assessments in the eDiary device and undergotraining.

• Participant meets modified Rome IV criteria for FC: For at least 1 month beforeScreening (Visit 1), the participant has had 2 or fewer defecations (with eachdefecation occurring in the absence of any laxative, suppository, or enema useduring the preceding 24 hours) per week. In addition, at least once per week,participant must meet 1 or more of the following:

• History of retentive posturing or excessive volitional stool retention.

• History of painful or hard bowel movements (BMs).

• Presence of a large fecal mass in the rectum.

• History of large diameter stools.

• At least 1 episode of fecal incontinence per week after the acquisition oftoileting skills, if applicable.

Exclusion Criteria:

• Participant history of:

• Celiac disease, or positive serological test for celiac disease or thecondition is suspected but has not been ruled out by endoscopic biopsy

• Cystic fibrosis

• Hypothyroidism that is untreated or treated with thyroid hormone at a dose thathas not been stable for at least 3 months prior to Screening (Visit 1)

• Down's syndrome or any other chromosomal disorder

• Active anal fissure (i.e., participant reports having streaks of blood on thestool or on toilet paper and/or pain/crying with BM within 2 weeks prior toScreening). (Note: anal fissures that have resolved at least 2 weeks prior toscreening would not be exclusionary.) However, if in the investigator'sopinion, an anal fissure(s) may be the primary cause of participant's modifiedRome IV FC criteria, the participant would not be eligible to participate inthe study.

• Anatomic malformations (e.g., imperforate anus, anal stenosis, anteriordisplaced anus)

• Intestinal nerve or muscle disorders (e.g., Hirschprung disease, visceralmyopathies, visceral neuropathies)

• Neuropathic conditions (e.g., spinal cord abnormalities, neurofibromatosis,tethered cord, spinal cord trauma)

• Lead toxicity, hypercalcemia

• Inflammatory bowel disease

• Childhood functional abdominal pain syndrome

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

• Lactose intolerance that is associated with symptoms which could confound theassessments in this study

• History of cancer. (Note: participants with a history of cancer are allowedprovided that the malignancy has been in a complete remission beforeRandomization (Visit 2). A complete remission is defined as the disappearanceof all signs of cancer in response to treatment.)

• Has conditions that could interfere with drug absorption including but not limitedto short bowel syndrome.