In a blow to Amgen Inc., the Food and Drug Administration has said it wants more safety information about the company’s experimental bone-strength drug Prolia before granting marketing approval.

The Thousand Oaks biotech wants to sell Prolia, also known as denosomab, for the treatment and prevention of postmenopausal osteoporosis. The FDA requested more information about how Amgen will monitor patients who use the drug, and wants the company to develop a strategy to evaluate the risks.

“We are confident that we can quickly respond to the FDA’s requests … and plan to do so in the near term,” Roger Perlmutter, Amgen’s executive vice president of research and development, said in a statement.

The company had hoped for FDA approval by the end of the year, and the new demands make that unlikely.

Regulators also asked for additional clinical data on the preventive therapy aspect of the drug’s use, but in a positive note for the company did not require more studies on its primary use as a treatment for existing osteoporosis.

Amgen said it expects an additional response from the FDA for its separate application to sell Prolia as a treatment for bone loss caused by hormone deprivation therapy, a smaller potential market for the drug.

The FDA in recent years has become increasingly cautious about first-in-class drugs such as Prolia. The caution follows a series of high-profile cases in which drugs – including Amgen’s second-generation anemia drug Aranesp — were found to increase the risk of death and serious injury in post-approval studies.

Amgen shares were down 93 cents, or 1.5 percent, to $60.16 in midday trading on Nasdaq.