An Open-Label, Long-term Study to Assess the Immunogenicity of LINZESS® (Linaclotide) Administered Orally to Adult Participants With Irritable Bowel Syndrome With Constipation or Chronic Idiopathic Constipation

Inclusion Criteria:

• Participants meet the Rome III criteria for IBS-C or CIC:

• IBS-C Criteria: the participant must meet the following 2 criteria (A and B). A. IBS Criteria: The participant must have abdominal pain or discomfort at least 3 days permonth in the 3 months before diagnosis (with symptom onset at least 6 months beforediagnosis) associated with 2 or more of the following:

1. Improvement with defecation.

2. Onset associated with a change in frequency of stool.

3. Onset associated with a change in form (appearance) of stool. B. Stool ConsistencyRequirement: During the 3 months before diagnosis in the absence of laxative or enemause, the patient has hard or lumpy stools (Bristol Stool Form Scale [BSFS] score 1 or

2. with at least 25% of bowel movements (BMs) and has loose or mushy stools (BSFS 5 or
3. with <25% of BMs.

• CIC Criteria: the participant must meet the following 3 criteria (A, B, and C): A. Participant meets 2 or more of the following criteria for 3 months before the diagnosiswith symptom onset at least 6 months before diagnosis:

1. Straining during at least 25% of defecations.

2. Lumpy or hard stools in at least 25% of defecations.

3. Sensation of incomplete evacuation for at least 25% of defecations.

4. Sensation of anorectal obstruction/blockage for at least 25% of defecations.

5. Manual maneuvers to facilitate at least 25% of defecations (e.g., digital evacuation,support of the pelvic floor).

6. Fewer than 3 defecations per week. B. Loose stools are rarely present without the useof laxatives. C. Insufficient criteria for irritable bowel syndrome. (The criteria forIBS are provided in Point A under IBS Criteria, above).

• Participant meets the colonoscopy requirements, which are modified from theSummary of the US-Multi-Society Task Force on Colorectal Cancer and otherColonoscopy Requirements.

• Participant has successfully completed protocol procedures (with no clinicallysignificant findings).

Exclusion Criteria:

• At Day 1 visit, the participant reports having 6 or more spontaneous bowel movements (SBMs) in the week prior to screening.

• At Day 1 visit, the participant reports having any SBMs that were watery (BSFS=7) ormore than 1 SBM that was mushy (BSFS=6) in the week prior to screening.

• Participant has a structural abnormality of the gastrointestinal (GI) tract or adisease or condition that can affect GI motility.

• Participant has any protocol excluded or clinically significant medical or surgicalhistory that would limit the patient's ability to complete or participate in thisclinical trial or could confound the study assessments.

• Participant has ever received linaclotide as a treatment (includingcommercially-available product) or has been randomized into any clinical study inwhich linaclotide was a treatment. (participant who enrolled into linaclotide clinicalstudies conducted prior or during this study but failed to be randomized are eligiblefor the current study).

• Participant has ever received plecanatide, SP-333, or has participated in aplecanatide clinical study.