A Phase 3 Study of Tenapanor to Treat Hyperphosphatemia in ESRD Patients on Dialysis

Inclusion Criteria: * Females must be non-pregnant, non-lactating, and either be post-menopausal for at least 12 months, have documentation of irreversible surgical sterilization, or confirm the use of one of the acceptable contraceptive methods * Males must agree to avoid fathering a child and agree to use an appropriate method of contraception * Chronic maintenance hemodialysis 3x a week for at least 3 months * Chronic maintenance peritoneal dialysis for a minimum of 6 months * Kt/V ≥ 1.2 at most recent measurement prior to screening * Prescribed and taking at least 3 doses of phosphate binder per day * Serum phosphorus levels should be between 4.0 and 8.0 mg/dL at screening * Unchanged dose of vitamin D or calcimimetics for the last 4 weeks prior to screening * For enrollment in the study after at least 2 weeks of wash-out, subjects must have serum phosphorus levels of at least 6.0 mg/dL but not more than 10.0 mg/dL and have had an increase of at least 1.5 mg/dL versus pre-wash out value after 2 or 3 weeks wash-out of phosphate binders Exclusion Criteria: * Severe hyperphosphatemia defined as serum phosphorus greater than 10.0 mg/dL on phosphate-binders at any time point during clinical routine monitoring for the 3 preceding months before screening visit * Serum/plasma parathyroid hormone \>1200 pg/mL * Clinical signs of hypovolemia at enrollment * History of IBD or IBS-D * Scheduled for living donor kidney transplant, change to peritoneal dialysis, home HD or plans to relocate to another center during the study period * Positive serology with evidence of significant hepatic impairment or WBC elevation according to the Investigator * Life expectancy \<6 months * Previous exposure to tenapanor