The speculation is now confirmed - Chris Viehbacher, who earlier this week announced he had left Glaxo’s board and would resign his job as head of the North American pharma unit in December, is taking the top job at Sanofi-Aventis.

Viehbacher, 48, will succeed Gerard Le Fur, 57, who became Sanofi’s ceo in January 2007 and will remain for an unspecified period of time as a scientific advisor, according to a statement.

The move comes as Sanofi experiences frustration in launching new products that can offset the looming patent loss of its older best-selling drugs. That has helped depress Sanofi shares, which are down 22 pressured from a year ago, and has pressured Le Fur.

With the looming patent expiration of two top-selling drugs, blood-thinner Plavix and the Lovenox blood clotter, the drugmaker needs new meds. The Ketek antibiotic Acomplia fat pill were once seen as potential blockbusters, but were stymied by links to side effects.

Along with the president of Glaxo’s pharma biz, David Stout, who left last February, Viehbacher was one of two execs who lost the recent race to succeed JP Garnier as Glaxo’s ceo, a position now held by Andrew Witty.