Thousand Oaks-based biotech giant Amgen said Thursday that it has named Ronald D. Sugar to the firm's board of directors. Sugar is the former Chairman of Northrop Grumman Corp, having served as Chairman and CEO of the defense firm from 2003 to 2009. Sugar also serves on the board of Chevron, and also has served at Litton Industries, TRW, and TRW Aerospace. The firm said the addition of Sugar brings the company's number of board directors to 14.