Amgen Inc. has purchased 49 percent of shares for Amgen Astellas BioPharma, the result of a 2013 joint venture between Japanese company Astellas Pharma and the Thousand Oaks biotech giant. Financial terms of buyout were not disclosed. Amgen Astellas Biopharma, renamed Amgen K.K., is now a wholly owned subsidiary of Amgen, the company said in a statement. The share purchase mirrors Amgen’s move in October to buy a 20.5 percent stake in Chinese cancer biotech Beigene for $2.7 billion in cash, also increasing its presence in Asia and advancing pipeline drugs. “Amgen medicines have been available for patients in Japan for many years through local partnerships, including most recently our joint venture with Astellas. Going forward, Amgen K.K. will continue marketing our treatments for patients with cardiovascular disease, cancer and osteoporosis, as well as new medicines emerging from our pipeline,” Steve Sugino, president of Amgen K.K., said in a statement. “As Amgen K.K., we will continue to work and invest to become an even more valuable member of the health care community in Japan.” Amgen has expanded its geographic presence from 50 to 100 countries since 2011. The company announced the share purchase late Tuesday. Shares of Amgen (AMGN) closed Wednesday down $4.92, or 2.4 percent, to $197.81 on the Nasdaq.