* Sanofi to buy back CVRs for up to $152 mln
* Will pay between $1.50 and $1.75 per CVR (Adds details, background)
PARIS, Sept 4 (Reuters) - Sanofi plans to buy back up to $152 million worth of certificates linked to the success of Genzyme drugs, a move that signals its growing confidence in Lemtrada, a multiple sclerosis that is awaiting approval from regulators.
The French drugmaker said on Tuesday it would buy about 30 percent of its outstanding contingent value rights (CVR) , which are linked to its 2011 purchase of U.S. biotech Genzyme, for between $130 and $152 million.
Lemtrada was the main sticking point in the protracted merger talks between Sanofi and Genzyme. At the time, Sanofi Chief Executive Chris Viehbacher's team was keen to talk down its prospects. Genzyme had projected peak Lemtrada sales of $3.5 billion a year, while Sanofi pitched the number at around $700 million.
The final deal between the two companies included a contingent value right, a tradeable security that gives payouts to Genzyme investors if certain revenue targets are met, to bridge their differences.
CVR holders could receive as much as $14 per CVR, or $3.8 billion, by the end of 2020 if Lemtrada meets its most ambitious sales targets.
The CVRs, however, have been trading at a significant discount to the $2.30 price they began trading at in April 2011 given the risks tied to a new drug that has yet to be approved.
Sanofi said it would pay between $1.50 and $1.75 per CVR, a premium of between 7.1 and 25 percent to their last price of $1.40 on Aug. 31. Its offer will run until Oct. 5.
Despite a recent setback at the U.S. Food and Drug Administration, when the regulator asked Sanofi to refile its marketing application for the drug, Lemtrada could be launched in 2013 if it wins approval.
It is one of the new products the French drugmaker is betting on to restore growth after losing several aging blockbusters to generic rivals.
The drug, chemically known as alemtuzumab, is already used under a different dosage to treat blood cancer under the brand Campath.
In a further sign of confidence in the prospects for Lemtrada, Sanofi has pulled Campath from the market, but will continue to provide it through patient access programs.
Sanofi shares were trading 0.7 percent lower at 66.06 euros at 0749 GMT, underperforming the CAC40 index, down 0.2 percent. (Reporting by Elena Berton and James Regan; Additional reporting by Ben Hirschler; Editing by Matt Driskill and Christian Plumb)