US regulators have turned down Amgen's request to market Parsabiv for secondary hyperparathyroidism (sHPT).

The biotech giant is seeking approval for the drug to treat the condition in adult patients with chronic kidney disease (CKD) who are receiving haemodialysis.

But after reviewing the data the US Food and Drug Administration has issued the firm with a Complete Response Letter turning down its application.

The contents have not been revealed, but Amgen says it anticipates a post-action meeting with the FDA later this year to discuss its response.

Secondary HPT is a common, serious and often progressive condition among patients with CKD. It develops in response to declining kidney function, when the parathyroid (PTH) glands increase the production of thyroid to maintain normal levels of calcium and phosphorus.

However, eventually this excess production is not enough to maintain normal levels, and at the point of CKD dialysis, this manifests as abnormal amounts of PTH, calcium and phosphorus that, in turn, can lead to significant clinical consequences, such as weakness and thinning of the bones.

Parsabiv (etelcalcetide) is a novel calcimimetic agent that suppresses the secretion of PTH by binding to and activating the calcium-sensing receptor on the parathyroid gland. The treatment is given intravenously three times per week at the end of each dialysis session.

The submission is based on data from three Phase III studies, one of which showed that 74 percent of patients given the drug experienced a greater than 30 percent reduction from baseline in PTH compared with 8.3 percent in the placebo arm.