By Nina Sovich and Noelle Mennella
PARIS (Reuters) - French drugmaker Sanofi-Aventis SA agreed to buy GENZYME (GENZ.NQ)Corp with a sweetened $20.1 billion cash offer, plus payments tied to the success of the U.S. biotech group's drugs, the companies said on Wednesday.
The acquisition -- which comes nine months after Sanofi CEO Chris Viehbacher first put the idea to Genzyme's Henri Termeer -- is expected to boost Sanofi's earnings from the first year after completion by giving it a new platform in rare diseases.
Sanofi will pay $74 a share in cash plus a tradable contingent value right, or CVR, whose value will depend on Genzyme's experimental multiple sclerosis drug Lemtrada and production volumes of two other medicines.
The deal, whose announcement confirmed what sources with knowledge of the talks had told Reuters on Tuesday, is the second-biggest in biotech history and will help Sanofi compensate for declining revenue from drugs that have lost, or are set to lose, patent protection.
Sanofi also predicted the deal, which is expected to close early in the second quarter, would lift its underlying, or "business," earnings by between 0.75 and 1.0 euro per share by 2013.
The $20.1 billion cash sum is based on 272.5 million Genzyme shares on a diluted basis.
The CVR runs until the end of 2020 and entitles holders to a series of payments worth up to $14 in total, depending mainly on the success of Lemtrada.
Its value in the market is expected to be deeply discounted given the long time horizons and the fact many short-term investors and index funds, which do not normally like owning this kind of instrument, are likely to move quickly to sell.
Market estimates that the CVR would trade at around $2-3 "may not be unrealistic," Viehbacher told reporters.
The first $1 related to the CVR will be paid out if specified production levels are met in 2011 for Cerezyme and Fabrazyme -- two drugs for Gaucher and Fabry disease.
The bulk of the potential payments, however, are linked Lemtrada and will kick in if that drug wins approval in multiple sclerosis and exceeds various sales milestones, which run up to $2.8 billion.
Viehbacher said the CVR structure served as an important "value bridge" and would reward both Genzyme and Sanofi shareholders, particularly if Lemtrada outperforms market expectations.
Genzyme was the first company to show that money could be made by making drugs for diseases with small patient populations. In 2009 it generated revenue of $4.5 billion, enough to replace roughly a third of the sales Sanofi is expected to lose through 2013 to generic competition.
Viehbacher said rare diseases represented a huge unmet need, with around 6,000 to 7,000 such disorders in the world for which there are treatments for only about 10 percent.
"It is a huge area of opportunity, which is why we are seeing a lot of companies coming in," he said.
Competition in the space is increasing but Viehbacher said Genzyme's position was extremely strong. "Genzyme is really the gold standard in patient-centric care and we believe the Genzyme brand will be able to protect that franchise," he said.
Wednesday's deal follows a lengthy stand-off between Viehbacher and Termeer, a Dutchman who has led the company for more than 25 years.
Termeer was reluctant to sell the company that had come to define him, but a manufacturing crisis caused a shortage of key Genzyme drugs -- leading to outrage among patients and investors alike -- and by May last year the company's shares had fallen 46 percent from a high of close to $84 in July 2008.
Sanofi made its first formal offer of $69 a share in August.
Credit Suisse and Goldman Sachs are advising Genzyme. Evercore Partners and JPMorgan are Sanofi's lead advisers.
(Additional reporting by Tim Hepher and Ben Hirschler; Editing by David Holmes)