An 8-Week Study to Evaluate Tenapanor in the Treatment of Hyperphosphatemia in End-Stage Renal Disease Patients on Hemodialysis (ESRD-HD)

Inclusion Criteria: * 18 to 80 years old * 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/week for at least 3 months * Kt/V ≥ 1.3 at most recent measurement prior to screening * Prescribed and taking at least 3 doses of phosphate binder per day * Serum phosphate levels should be between 4.0 and 7.0 mg/dL (inclusive) at screening * For randomization in the study, after 1 week wash-out of phosphate binders, subjects must have serum phosphate level of at least 9 mg/dL but below 10 mg/dL and have had an increase of at least 1.5 mg/dL versus pre-wash out value * For randomization in the study, after 2 or 3 weeks wash-out of phosphate binders, subjects must have serum phosphate level of at least 6 mg/dL but below 10 mg/dL and have had an increase of at least 1.5 mg/dL versus pre-wash out value Exclusion Criteria: * Severe hyperphosphatemia defined as \>10 mg/dL on Phosphate-binders at any time point during clinical routine monitoring for the 3 preceding months before screening * Serum parathyroid hormone \>1200 pg/mL * Persistent metabolic acidosis defined as serum carbon dioxide \<18 mmol/L from two consecutive measurements during screening and washout periods * Clinical signs of hypovolemia at randomization * History of inflammatory bowel disease (IBD) or diarrhea predominant irritable bowel syndrome (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 * Diarrhea or loose stools during the week before randomization defined as BSFS ≥ 6 and frequency ≥ 3 for 2 or more days * Any evidence of or treatment of malignancy within one year, excluding non-melanomatous malignancies of the skin * Positive serology with evidence of significant hepatic impairment or WBC elevation according to the Investigator * Life expectancy \< 6 months