Jonathan Peacock, the chief financial officer of Amgen Inc., stepped down from his position Friday but will remain with the company until May to assist in the transition. The Thousand Oaks drug giant announced late Thursday that Peacock is leaving to “pursue broader career opportunities.” The company has named Michael Kelly as acting chief financial officer. “Since joining Amgen over three years ago, Jon has played an important role in developing and implementing the company’s strategy for growth and in delivering value for shareholders,” said Chief Executive Robert Bradway, in a statement. Kelly has been at Amgen since 2003, working in international commercial operations and chief accounting officer. In his interim position, he will supervise all accounting and investor relations operations. Shares closed down 90 cents, or a fraction of a percent, to $117.99 on the Nasdaq.