Litchfield, who joined the company's UK business in 1990, is currently responsible for treasury, tax and investor relations. In the past, she has also led financial operations for Human Health, which is Merck's largest business.

Last month, the company had said Ken Frazier would step down as chief executive officer at the end of June and be replaced by Davis.

(Reporting by Dania Nadeem in Bengaluru; Editing by Krishna Chandra Eluri)