Chris Viehbacher, head of GlaxoSmithKline’s North American pharmaceutical operations, is poised to join Sanofi-Aventis as a top executive, signalling an important shake-up at the French medicines group.

Sanofi-Aventis’s shares were up as much as 5.2 per cent on Wednesday, having gained as much as 4 per cent on Tuesday on reports of Mr Viehbacher’s move. The news took senior executives at the French group by surprise, and its press office said on Tuesday that it had no information.

However, individuals with knowledge of Mr Viehbacher’s move indicated that in early December he would be joining Sanofi-Aventis, which has seen a 20 per cent drop in its share price over the past year.

His appointment, if confirmed, would probably threaten the position of Gerard Le Fur, the chief executive appointed at the start of 2007 when the role was split from that of chairman, held by Jean-Francois Dehecq.

Les Echos, the French newspaper, reported that Mr Viehbacher would replace Mr Le Fur as chief executive.

That would require careful negotiation on any division of powers with Mr Dehecq, a colourful executive who built Sanofi-Aventis through a succession of mergers over the past three decades and who remains a pivotal influence on the group.

The selection of Mr Viehbacher, who holds German and Canadian citizenship, would also mark a radical departure for Sanofi-Aventis, which has in the past benefited from close political support from the French authorities and has promoted top executives from within.

But Sanofi-Aventis has faced growing investor pressure in recent months, with both of its core French corporate shareholders – Total and L’Oréal – indicating that their strategic stakes could be sold, and the latter already disposing of part of its holding.

Amit Roy, European pharmaceuticals analyst at Citigroup in London, who wrote a note on Tuesday ahead of the news expressing little justification for an upgrade, said: “If it’s true, this would be a big cultural shift for Sanofi.”

Mr Viehbacher is one of the most senior executives at GSK, who lost out last year in the race against two other insiders to succeed Jean-Pierre Garnier on his retirement in May.

He was then offered a £2.5m retention bonus in shares, a pay rise to $800,000 a year and a boardroom seat, providing an indication of the likely seniority and remuneration he will have to receive at Sanofi-Aventis to compensate.

He spent a decade in France working for and then running the local office of Glaxo Wellcome ahead of its merger into GSK.

He represented the industry on the European Commission’s G10 high-level working group on the competitiveness of the pharmaceutical sector, and was awarded France’s Légion d’Honneur in 2003.

Mr Le Fur has broadened the executive management team, diversified into biological medicines and launched a series of share buy-backs.

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