This study is designed to evaluate efficacy and safety of KHK7580 orally administered once daily for 32 weeks for patients with secondary hyperparathyroidism receiving peritoneal dialysis. After 32-week treatment period, the subjects will receive KHK7580 in the 20-week extension period to evaluate long-term safety and efficacy.

Inclusion Criteria:

• Personally submitted written voluntary informed consent to participate in the study
• Stable chronic renal disease treated with peritoneal dialysis for at least 16 weeks before screening
• Intact PTH level of > 240 pg/ml at screening

Exclusion Criteria:

• Treatment with cinacalcet hydrochloride within 2 weeks before screening;
• Change in dose or dosing regimen of an activated vitamin D drug or its derivative, phosphate binder, or calcium preparation within 2 weeks before screening; or start of treatment with such drugs within 2 weeks before screening;
• Parathyroidectomy and/or parathyroid intervention within 24 weeks before screening;
• Severe heart disease;
• Severe hepatic dysfunction;
• Uncontrolled hypertension and/or diabetes;
• Treatment with an investigational product (drug or medical device) in a clinical study or any study equivalent to clinical study within 12 weeks before screening;
• Primary hyperparathyroidism;
• Other conditions unfit for participation in this study at the discretion of the investigator or subinvestigator.