Feb 7 (Reuters) - The U.S. Food and Drug Administration has approved Amgen Inc's treatment for secondary hyperparathyroidism in adult patients with chronic kidney disease undergoing dialysis, the U.S. biotech company said on Tuesday.

The drug, etelcalcetide, will be sold under the brand name Parsabiv, Amgen said, adding that it is the first new therapy approved for the condition in 12 years.

It is designed to be administered intravenously three times a week at the end of a dialysis session.

Secondary hyperparathyroidism is a serious chronic condition that affects a high percentage of kidney disease patients receiving dialysis. It involves excessive secretion of parathyroid hormone by the parathyroid glands in response to decreased kidney function.

Parsabiv mimics the action of calcium by activating calcium-sensing receptors on the parathyroid gland to decrease levels of parathyroid hormone.

Annual sales of the drug are forecast to exceed $600 million by 2023, according to Thomson Reuters data.

(Reporting by Bill Berkrot; Editing by Jonathan Oatis)