Long Term Safety Study of Plecanatide

This is a phase 3, multicenter, open-label, long-term safety and tolerability study of 6 mg daily dose of plecanatide administered orally. Patients who are Study Completers or Eligible Screen Failures whose eligibility is confirmed at the end of their participation in the double-blind plecanatide studies SP304203-04 or SP304203-05 will be enrolled. Beginning on Day 1, patients will take one (1) plecanatide 6.0 mg tablet in the clinic and thereafter every morning with approximately 240 mL (8 ounces) of liquid, with or without meals. Safety and tolerability assessments and patients' self-assessment of disease severity will be performed according to the Schedule of Assessments. Patients who discontinue early from the study will undergo an Early Withdrawal (EW) visit within 5 days after stopping study drug.