Sanofi S.A. is a French multinational pharmaceutical company headquartered in Paris, France, as of 2013 the world's fifth-largest by prescription sales. The company was formed as Sanofi-Aventis in 2004 by the merger of Aventis and Sanofi-Synthélabo, which were each the product of several previous mergers. It changed its name to Sanofi in May 2011. The company is a component of the Euro Stoxx 50 stock market index.Sanofi engages in the research and development, manufacturing and marketing of pharmaceutical drugs principally in the prescription market, but the firm also develops over-the-counter medication. The company covers seven major therapeutic areas: cardiovascular, central nervous system, diabetes, internal medicine, oncology, thrombosis and vaccines (it is the world's largest producer of the latter through its subsidiary Sanofi Pasteur).