The rumour mill is buzzing again amid reports that Sanofi-Aventis has made an informal approach to acquire troubled Genzyme Corp.

The Wall Street Journal cited people familiar with the matter as saying that the two sides have begun sounding out each other's interest in a deal before entering into formal talks. However they also note that any final agreement is a long way off.

Unsurprisingly, Sanofi and Genzyme are making no comment on the report but equally an offer from the French drugmaker would not be a surprise given the high number of deals it has made since Chris Viehbacher has signed off since taking over as chief executive in 2008. That Genzyme is a target is also a logical step, given the problems the company has had since its Allston Landing facility in Boston was temporarily shut down last year after a bioreactor was contaminated with a virus.

This affected production of Cerezyme (imiglucerase) for Gaucher disease and Fabrazyme (agalsidase beta) for Fabry disease. Then, in November, the FDA warned of the potential for foreign particle contamination in all lots of the two aforementioned therapies plus Myozyme (alglucosidase alpha) for Pompe disease, Aldurazyme (laronidase) for mucopolysaccharidosis type I and Thyrogen (thyrotropin alpha) for thyroid cancer.

Those problems persist and Genzyme has lost over a third of its value in the past couple of years and its market capitalisation before Sanofi’s interest was reported was about $14 million. However news of an approach from Paris, however informal, pushed the US biotech’s stock up over 15%.

The WSJ sources claim that Genzyme would be looking at a bid of around $20 billion reflecting the potential for a turnaround. Sanofi was previously reported as having set aside $20 billion for a US acquisition so analysts believe there could be some truth in the rumour.

The WSJ later reported that GlaxoSmithKline has made a "very casual approach" to Genzyme, while some observers believe that the biotech giant Amgen may fancy a link-up.