Shares of Amgen Inc. gained nearly 13 percent on Monday in reaction to strong indications that it will win FDA approval for its osteoporosis drug.

The Thousand Oaks-based biotechnology company said late Friday that a late-stage study showed the osteoporosis drug denosumab significantly reduced the risk of bone fracture in post-menopausal women.

Full data from the study will not be released until a medical conference in September, making it unclear how denosumab's potential benefit in reducing fractures stacks up in comparison to existing drugs, Amgen said.

Amgen also said on Friday that the rates of denosumab’s side effects, including serious infections, were similar to a placebo that was used in the trial, relieving analyst worries that safety issues might scuttle the drug.

Amgen will report second quarter earnings Monday after the market closes.

Shares in Amgen were up more than 12 percent Monday to $60.54.