McDonald's Corp, the world's largest restaurant chain, will replace CEO Don Thompson with one of his top lieutenants following the company's worst US sales slump in more than a decade. Chief Brand Officer Steve Easterbrook will take the reins when Thompson steps down on March 1, the Oak Brook, Illinois-based company said in a statement Wednesday. Easterbrook, currently a senior executive vice president, also will join the board, filling Thompson's vacated seat, the company said.