This is an intra-individual titration study of KRN1493 to evaluate the safety and efficacy of KRN1493 for the treatment of hypercalcemia in patients with parathyroid carcinoma or intractable primary hyperparathyroidism (PHPT).

Inclusion Criteria:

• Patients who meet any one of the following. Patients with a diagnosis of parathyroid carcinoma and corrected serum calcium > 11.3 mg/dL at the latest screening test. Patients with intractable PHPT (defined as follows: impossible to localize parathyroid tumor before initial surgery or in relapse after surgery, or impossible to perform parathyroidectomy (PTx) for complications, and corrected serum calcium is > 12.5 mg/dL at the screening test).
• Patients who provided their voluntary written informed consent to participate in the study.

Exclusion Criteria:

• Patients diagnosed with malignant tumor except for parathyroid carcinoma, nonmelanoma skin cancer, and carcinoma in situ of the cervix within 5 years before enrollment.
• Patients receiving anticancer chemotherapy except for the treatment of parathyroid carcinoma.
• Patients diagnosed with hypercalcemia associated with malignant tumors other than parathyroid carcinoma.
• Patients who had hypersensitivities to cinacalcet HCl preparations or vehicles.