A Study to Assess Adverse Events and Change in Disease Activity in Pediatric Participants (Age 6 Months to <2 Years) With Functional Constipation Who Are Treated With Linaclotide

Inclusion Criteria:

• Individuals must be 6 months to less than 1 year and 11 months old, at the time thelegally authorized representative (LAR)/parent/guardian signs the informed consentin alignment with local requirements.

• The LAR/parent/guardian who will be completing the electronic diary (eDiary) is ableto read and understand the assessments in the eDiary device and must undergotraining.

• Participant meets Rome IV criteria for functional constipation (FC): for at least 1month before Screening (Visit 1), the participant must meet 2 or more of thefollowing:

• 2 or fewer defecations per week (with each defecation occurring in the absenceof any laxative, suppository, or enema use during the preceding 24 hours)

• History of excessive stool retention

• History of painful or hard bowel movements (BMs)

• History of large-diameter stools

• Presence of a large fecal mass in the rectum

• LAR/Parent/Guardian is willing to discontinue any laxatives used before thePreintervention Visit in favor of the protocol-permitted rescue medicine.

Exclusion Criteria:

• Participant has conditions that could interfere with drug absorption, including, butnot limited to, short bowel syndrome.

• History of clinically significant medical conditions or any other reason that theinvestigator determines would interfere with the individual's participation in thisstudy or would make the participant an unsuitable candidate to receive study drug.

• Participant has 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 (investigator has confirmed an active anal fissure andparticipant reports known anal fissure symptoms [i.e., streaks of blood on thestool or on diaper or toilet paper and pain/crying with bowel movement within 2weeks prior to Screening]). (Note: Anal fissures that have resolved at least 2weeks prior to screening would not be exclusionary). However, if in theinvestigator's opinion, an anal fissure(s) may be the primary cause ofparticipant's Rome IV FC criteria, the subject would not be eligible toparticipate in the 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

• 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 beforeenrollment/randomization (Visit 3). A complete remission is defined as thedisappearance of all signs of cancer in response to treatment)