David D. Arnold, president of the American University in Cairo, is leaving the institution to become the chief executive of the Asia Foundation. The Asia Foundation, which operates aid programs in 18 nations in the Asia-Pacific region, said in a statement that Mr. Arnold would officially join the nonprofit organization in January. He will replace the foundation’s current leader, Douglas Bereuter, who is retiring. Mr. Arnold has been president of the American University for seven years, overseeing the construction of a $400-million campus in the suburbs of Cairo and a $125-million fund-raising campaign, the largest in the institution’s history.