To investigate the safety of repeated administration of KHK7791 for 52 weeks while switching from a phosphate-binding agent to KHK7791 in Hemodialysis patients with hyperphosphatemia.

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 hemodialysis 3 times per week for at least 12 weeks until screening examination.
4. Dialysis conditions excluding dry weight, 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 4 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.
8. Kt/V urea ≥ 1.2 at the most recent test in routine medical practice before screening examination.

Exclusion Criteria:

1. Peritoneal dialysis was performed within 12 weeks before screening examination.
2. iPTH > 600 pg/mL (should be based on the most recent value from patient's medical records before pre-enrollment)
3. History of inflammatory bowel disease (IBD) or diarrhea predominant irritable bowel syndrome
4. History of gastrectomy or enterectomy (excluding endoscopic resection and cecectomy) or having undergone gastrointestinal tract surgery within 3 months before screening examination.
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. Severe heart disease, hepatic impairment, or concurrent cirrhosis.
8. Developed cerebrovascular disease or cardiovascular disease requiring hospitalization within 6 months before screening examination.
9. Uncontrollable hypertension or diabetes
10. Subjects experienced more than 3 times diarrhea or loose stool in a day at least six BSFS score more than two days in a week.
11. Scheduled for living donor kidney transplant, change in the mode of dialysis, home hemodialysis or plans to change the dialysis center (relocate to another hospital/clinic) during the study period.
12. Any diagnosis of or treatment of malignancy within 5 years before screening examination.

The datasets generated and/or analyzed during the study sponsored by Kyowa Kirin will be available in the Vivli repository, https://vivli.org/ourmember/kyowa-kirin/ as long as conditions of data disclosure specified in the policy section of the Vivli website are satisfied.