Amgen Inc. on Thursday said it would pay GlaxoSmithKline more than $275 million to get out of a co-marketing agreement with the British drug company to promote Amgen’s osteoporosis drug Prolia in certain regions outside the United States.

The Thousand Oaks biotech giant said in a regulatory filing that it would take over the marketing of Prolia in the European Union, Switzerland, Norway, Russia and Mexico by the end of the year. GlaxoSmithKline will continue to market the drug in Australia. In addition to the $275 million early-termination payment, Amgen will reimburse the company $15 million for costs incurred during the transition period.

Amgen signed the co-marketing deal in July 2009. The U.S. Food and Drug Administration approved Prolia, also known as denosumab, for use by postmenopausal women at risk of osteoporosis. The company also markets denosumab under the trade name Xgeva to fight bone loss in prostate cancer patients.

Amgen shares closed down $1.85, or 1.5 percent, to $124.13 on the Nasdaq.