Thousand Oaks-based Amgen, the largest biotech company in the country and the tri-county region’s biggest private employer, announced June 1 that a major bone strength drug was approved by the U.S. Food and Drug Administration to treat osteoporosis in postmenopausal women.

The approval is a breakthrough for Amgen, as analysts and investors have pinned their hopes on Prolia as the firm’s next blockbuster drug. Sales from its other flagship lines have fallen amid safety concerns, and investors have displayed concern about the company’s drug pipeline as the clock runs out on its patents.

Prolia had already received U.S. approval to treat some cancers, and European regulators last week approved it as a therapy for bone loss from prostate conditions in men. But the sheer numbers of post-menopausal women who have osteoporosis and are at risk for fracture make it a far bigger potential market.

Prolia will cost $825 per 60 milligram injection, Amgen said.

“We have priced Prolia responsibly while reflecting its strong therapeutic value and expect to make it commercially available in the U.S. within the next week,” Amgen Cheif Operating Officer Robert Bradway said in a news release.

The approval was announced after the markets closed. Amgen’s shares rose more than 3 percent to $52.46 in after-hours trading.

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