This presentation contains forward-looking statements regarding Genzyme's financial outlook and business plans and strategies, including without limitation our: ability to maximize the value of alemtuzumab in MS, including the expectation that alemtuzumab will redefine the MS treatment paradigm; expectation that alemtuzumab will fill unmet patient needs and will be more efficacious than other available treatments; expectation that adverse events related to the use of alemtuzumab will be manageable; projections for alemtuzumab global revenues and patient numbers; expected market share/penetration for alemtuzumab and forecasts for adoption by physicians and the marketplace; expectations regarding the pharmacoeconomic benefit of alemtuzumab; belief that a value-based pricing is achievable in the US and EU; and expected timelines for results of the phase 3 clinical trials. These statements are subject to risks and uncertainties that could cause actual results to differ materially from those forecasted. These risks and uncertainties include, among others: the possibility that phase 3 trials may be delayed or will not support the same conclusions as phase 2; the risk that alemtuzumab will not receive regulatory approvals on the timeframes expected or at all; the possibility that alemtuzumab revenues and market share/penetration will not achieve projected levels, including as a result of the inaccuracy of underlying modeling assumptions; the risk that alemtuzumab will not be as efficacious or as safe as expected or that physicians and the marketplace will not adopt alemtuzumab to the extent expected; the risk that pricing will not be supported at projected levels; the risk that Genzyme will not be able to implement its business plans with respect to maximizing the value of alemtuzumab in the market; and the risks and uncertainties described in Genzyme's SEC reports filed under the Securities Exchange Act of 1934, including the factors discussed under the caption "Risk Factors" in Genzyme's Quarterly Report on Form 10-Q for the period ended September 30, 2010. Genzyme cautions investors not to place substantial reliance on the forward-looking statements contained in this presentation. These statements speak only as of December 20 2010, the date of the presentation and Genzyme undertakes no obligation to update or revise the statements.

Important Information

Genzyme has filed with the Securities and Exchange Commission a Solicitation/Recommendation Statement on Schedule 14D-9 relating to the tender offer by Sanofi-Aventis. Genzyme shareholders are advised to read the company's Solicitation/Recommendation Statement on Schedule 14D-9 because it contains important information. Shareholders may obtain a free copy of the Solicitation/Recommendation Statement on Schedule 14D-9, as well as any other documents filed by Genzyme in connection with the tender offer, free of charge at the SEC's website at http://www.sec.gov. In addition, investors can obtain free copies of these documents from Genzyme by directing a request to Genzyme at 500 Kendall Street, Cambridge, MA 02142, Attention: Shareholder Relations Department, or by calling 617-252-7500 and asking for the Shareholder Relations Department.