Genzyme Corp. announced today that ongoing discussions with Sanofi-Aventis
have progressed to the point where Genzyme’s board has authorized the company
to enter into a confidentiality agreement with Sanofi-Aventis in order to allow
Sanofi to conduct due diligence.

Discussions between Genzyme’s advisors and Sanofi’s advisors
and between Genzyme and Sanofi representatives are continuing. These discussions
have focused to a significant degree on the potential use of a contingent value
right for alemtuzumab as a part of a potential resolution of the differences in
valuation between the parties, and the parties have also discussed other
potential terms for a negotiated transaction.

Genzyme can provide no assurance that discussions with
Sanofi will result in a transaction that will be determined by its board to be
in the best interests of the company and its shareholders.