Amgen Inc. reportedly is considering a bid to purchase cancer therapy company Medivation Inc. of San Francisco. The Thousand Oaks biotech would be competing with other drug giants interested in making the same acquisition, including Pfizer of New York City, Sanofi of Paris and AstraZeneca of London. Amgen is currently in talks with advisers as it decides whether to move forward with an offer, according to Bloomberg News. Sanofi already has made an unsolicited bid of $9.3 billion, or $52.50 a share, which some analysts felt was an undervaluation of the company. In response, Medivation rejected the bid. Amgen shares closed up 7 cents, or a fraction of a percent, to $154.25 on the Nasdaq.