Sanofi-Aventis named Elias Zerhouni as its new head of research and development as the French drugmaker reshapes its drug portfolio to offset sales losses from patent expiries.

Sanofi said on Tuesday Zerhouni, appointed as scientific adviser to Chief Executive Chris Viehbacher in 2009, had been "instrumental in redesigning the R&D model to foster increased innovation, the first pillar of the group's strategy."

Zerhouni will take over from Marc Cluzel as of Jan. 1 next year, Sanofi said in a statement on Tuesday. Cluzel will stay as a scientific expert to Zerhouni.

Sanofi is trying to buy U.S. biotech Genzyme in a $18.5 billion tender offer that it prolonged on Monday.

Buying Genzyme, which has turned down Sanofi's offer, would give Sanofi a new and high-margin growth area of rare diseases as mounting generic competition will take out roughly a third of Sanofi's 2008 sales base by 2013.