Chairman Richard T. Clark will retire from Merck’s board of directors effective December 1st. Mr. Clark led the company for five years as president and chief executive officer from 2005 through 2010. He has served as a director since May 2005 and chairman since 2007. Kenneth C. Frazier, Merck’s president and chief executive officer and board member — appointed this past January— has been elected to serve as chairman. Speaking on behalf of Merck’s board of directors, William B. Harrison, l...