FDA letter delays OK for Amgen bone drug Prolia

Amgen Inc. said Monday that the Food and Drug Administration wants more information about its osteoporosis treatment Prolia before granting marketing approval. It delays a drug seen as a potential blockbuster for the company.

In a letter, the FDA said it wants to know how Amgen will monitor patients who use Prolia and wants the company to develop a strategy to evaluate the risks of the drug, Amgen said.

Amgen shares fell $1.08 to $60.24.

The Thousand Oaks company wants to market Prolia for the prevention and treatment of postmenopausal osteoporosis. The FDA said Amgen needs to run more clinical tests of Prolia as a preventive therapy, but Amgen will not have to perform further testing of Prolia as a treatment for the illness.

Prolia, which is also called denosumab, works by targeting cells that break down bone.

Amgen said it was reviewing the FDA’s message, called a complete response letter, and planned to respond soon.