Paul Covington, M.D. is retiring as executive vice president of development and chief medical officer of PPD, Inc., effective June 30. He will serve as a special project adviser through January 2009 to assist with selected projects and the transition of his responsibilities.     “Paul is one of the most talented physicians in our industry, and his leadership and unwavering commitment to excellence have played a significant role in the continued growth and success of our company,” said Fred Es...