Clinical Study of KHK7791 in Hyperphosphatemia Patients on Peritoneal Dialysis

Inclusion Criteria: 1. Has voluntarily provided written informed consent to participate in the study. 2. Aged ≥ 20 years (expressed in completed years) at the time of providing informed consent. 3. Stable chronic renal failure patients who have undergone peritoneal dialysis 3 times per week for at least 12 weeks until screening examination. 4. Dialysis conditions, should have been unchanged during the last 2 weeks before screening examination. 5. The prescribed drug and dosage regimen should have been unchanged during the last 2 weeks before screening examination. 6. Serum phosphorus levels should be in the range of ≥ 3.5 and ≤ 7.0 mg/dL at screening examination. 7. If on any vitamin D, calcimimetics regimen, bisphosphonate,calcitonin preparations, selective estrogen receptor modulators or teriparatide preparations then the prescribed drug and dosage regimen should have been unchanged for the last 4 weeks before screening examination. Exclusion Criteria: 1. Subjects who received concomitant hemodialysis or hemodialysis filtration within 12 weeks before screening examination. 2. Having concurrent or a history of inflammatory bowel disease (IBD) or diarrhea-predominant irritable bowel syndrome 3. History of gastrectomy or enterectomy or having undergone gastrointestinal tract surgery within 3 months before screening examination. 4. Subjects in whom peritonitis, catheter-related infections, catheter dysfunction, etc. are confirmed within 4 weeks before screening examination., and the continuation of peritoneal dialysis is considered to be interfering with the implementation of peritoneal dialysis. 5. Subjects who used anti RANKL preparations within 6 weeks before screening examination. 6. Subjects who used anti-sclerostin antibody preparations within 12 weeks before screening examination. 7. Having concurrent severe heart disease or hepatic impairment. 8. Developed cerebrovascular disease or cardiovascular disease requiring hospitalization within 6 months before screening examination. 9. Subjects who have undergone parathyroid intervention within 24 weeks before screening examination., or subjects who are scheduled to undergo parathyroid intervention between the implementation of the pretest and the completion of the study. 10. Uncontrollable hypertension or diabetes. 11. Scheduled for living donor kidney transplant, change in the mode of dialysis, home hemodialysis, or change in the dialysis center (relocate to another hospital/clinic) during the study period. 12. Any diagnosis of and treatment of malignancy within 5 years before screening examination.