Primary HPT involves autonomous oversecretion of parathyroid hormone (PTH), usually by a tumor of the parathyroid gland. Elevated PTH levels result in an increase in serum calcium concentration. Primary HPT can be caused by adenoma, hyperplasia, or parathyroid carcinoma. Parathyroidectomy (PTx) is the only reliable method to treat primary HPT including parathyroid carcinoma. Control of hypercalcemia can prove challenging in cases of primary HPT where PTx is not an option because of concomitant diseases or where primary HPT recur after PTx and parathyroid carcinoma, although patients with such hypercalcemia are very rare. An effective treatment is needed for hypercalcemia, as it causes symptoms of fatigue, polyuria, thirst, and renal impairment and severe hypercalcemia can result in death due to a hypercalcemic crisis.
*2: Review Committee on Unapproved Drugs and Indication with High Medical Needs
The Committee was established for the purpose of enhancing development by the pharmaceutical companies of drugs and indications that have been approved for use in the United States and Europe but not yet approved in Japan, through activities such as eva luating medical needs and confirming the applicability of "Application based on evidence in the public domain" and investigating the need for studies that should be additionally conducted.
*3: Orphan drug designation
A drug must meet the following three conditions in order to be granted an orphan drug designation in Japan.
1) The number of patients who may use the drug is less than 50,000 in Japan.
2) There are high medical needs for the drug (There is no appropriate alternative drug/treatment, or high efficacy or safety is expected compared with existing products).
3) There is high possibility of development (There should be a theoretical rationale for the use of the drug for the target disease, and the development plan should be appropriate). For designated orphan drugs, measures to support the research and development activities are taken (The orphan drug and orphan medical device research and development promotion program).
