The waiting is over and Sanofi-Aventis is to acquire Genzyme Corp for $20.1 billion, nine months after its first approach.

The French drugmaker has upped its offer from $69 per share, or $18.50 billion, to $74 per share in cash. In addition, the deal includes a tradable contingent value right (CVR), entitling Genzyme shareholders to payments linked to the success of  Lemtrada (alemtuzumab), an experimental drug for multiple sclerosis.

The agreement also allows for milestones linked to production volumes in 2011 for Cerezyme (imiglucerase) for Gaucher disease and Fabrazyme (agalsidase beta) for Fabry disease, which have been severely affected by manufacturing problems.

Sanofi chief executive Chris Viehbacher said the transaction will create "a meaningful new growth platform" for the firm, "while expanding our footprint in biotechnology". He added that the CVR structure, "which served as an important value bridge between our two companies", rewards both Genzyme and Sanofi shareholders, "particularly if Lemtrada outperforms the market’s current expectations.”

John Shortmoor, an analyst at Datamonitor, said "this is a great deal for Sanofi, paying close to their original budget". He added that the firm gained access to niche markets "where competition is limited by more than just patent protection, providing a platform for long-term sales growth, diversifying away from the traditional blockbuster model". Mr Shortmoor went on to say that Sanofi is in a good position to extend the geographic reach of Genzyme's portfolio, especially in growth markets.

The transaction, which has been unanimously approved by the boards of directors of both companies and been given the regulatory green light in the USA and Europe, is expected to close early in the second quarter. It is expected to be accretive to the Paris-headquartered firm's business net earnings per share in the first year and lift profits by 0.75–1.00 euro per share by 2013. 

The firms will hold a conference call later today and give more details about the deal.