PARIS ( TheStreet) -- Sanofi ( SNY), the French drugmaker, has reached an agreement in principle on the outlines of a deal to buy Genzyme ( GENZ), according to multiple reports. The deal will include a contingent value right based on the performance of Genzyme's Lemtrada, a multiple sclerosis drug, Reuters reports, citing sources. A CVR gives shareholders an added benefit if an acquired company hits a future benchmark. Sanofi and Genzyme, the U.S. biotechnology company, could reach a deal within a week or two, Reuters reports. Just last week, Sanofi said "significant differences" remained on the potential CVR. Sanofi's offer of $69 a share, or $18.5 billion, for Genzyme ends on Feb. 15. Sanofi and Genzyme disclosed earlier Monday in a regulatory filing that Sanofi has begun due diligence on Genyzme's books. -- Written by Joseph Woelfel >To contact the writer of this article, click here: Joseph Woelfel >To submit a news tip, send an email to: email@example.com.