Myozyme Produced at the 2000 L Bioreactor Scale to Receive Accelerated Approval

Date: November 17, 2008

New PDUFA Date Set for February 28, 2009

Genzyme Corporation (Nasdaq: GENZ) today announced that the FDA plans an Accelerated Approval for Myozyme® (alglucosidase alfa) produced at the 2000 L bioreactor scale for the treatment of Late Onset Pompe disease. The company and the agency first need to agree on the design of a post-approval verification study and the FDA must complete its review of the Risk Evaluation and Mitigation Strategy (REMS) for the product. Genzyme submitted the REMS earlier this month. The FDA has classified this submission as a major amendment to the BLA for Myozyme produced at the 2000 L scale, and therefore has extended the PDUFA date by 90 days to February 28, 2009. Genzyme will be required to submit the final protocol for the verification study after approval.

Genzyme does not expect this extension to affect its 2009 non-GAAP earnings per share. The company reconfirmed its non-GAAP earnings guidance of $4.70 per share for next year.

“We’re very pleased to have additional clarity from the FDA on what it will take for 2000 L-scale product approval,” said Genzyme’s Senior Vice President of Global Market Access Alison Lawton. “The ongoing communication with the FDA has been positive, and the agency has done a substantial amount of work in a short time to facilitate approval of this product for patients.”

Myozyme is a treatment for Pompe disease, a progressive, debilitating and life-threatening inherited disorder affecting approximately 2,000 people in the United States. Genzyme currently has U.S. approval to sell Myozyme produced at the 160 L bioreactor scale, and the company has been seeking clearance from the FDA for 2000 L-scale production. Genzyme submitted a separate BLA for alglucosidase alfa produced using the 2000 L manufacturing process on May 30, following a determination by the FDA that alglucosidase alfa produced at the 160 L and 2000 L scales should be considered as two separate products because of comparability differences.

On October 21, 2008, the FDA’s Endocrinologic and Metabolic Drugs Advisory Committee affirmed by a 16 to 1 vote that the Late-Onset Treatment Study established effectiveness of the 2000 L-scale product for the treatment of Pompe disease. A majority of the committee members supported Accelerated Approval (Subpart E). As part of the accelerated approval procedure, a verification study is required to demonstrate clinical benefit of the 2000 L-scale product during the post-marketing period.

About Genzyme

One of the world’s leading biotechnology companies, Genzyme is dedicated to making a major positive impact on the lives of people with serious diseases. Since 1981, the company has grown from a small start-up to a diversified enterprise with more than 10,000 employees in locations spanning the globe and 2007 revenues of $3.8 billion. In 2007, Genzyme was chosen to receive the National Medal of Technology, the highest honor awarded by the President of the United States for technological innovation.

With many established products and services helping patients in nearly 90 countries, Genzyme is a leader in the effort to develop and apply the most advanced technologies in the life sciences. The company’s products and services are focused on rare inherited disorders, kidney disease, orthopaedics, cancer, transplant and immune disease, and diagnostic testing. Genzyme’s commitment to innovation continues today with a substantial development program focused on these fields, as well as cardiovascular disease, neurodegenerative diseases, and other areas of unmet medical need.

Genzyme’s press releases and other company information are available at and by calling Genzyme’s investor information line at 1-800-905-4369 within the United States or 1-678-999-4572 outside the United States.

This press release contains forward-looking statements regarding Genzyme’s business plans and strategies, including without limitation: its expectations regarding receipt of accelerated approval from the FDA of the alglucosidase alpha 2000 L process BLA, and the timing thereof; its expectation that the PDUFA date extension will not affect its 2009 non-GAAP EPS; and its expectations regarding the FDA’s willingness to grant accelerated approval once it reviews the Company’s REMS and agrees with the Company on the design of a verification study. 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: that the FDA does not grant accelerated approval of the alglucosidase alpha 2000 L process on or before February 28, 2009 due to concerns regarding product safety or efficacy, the adequacy of the Company’s risk mitigation strategy, disagreement over the appropriate indication for use, inadequate staffing at the agency, or for any other reason; that the financial impact of the delay in approval is greater than expected; 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 10Q for the quarter ended September 30, 2008. Genzyme cautions investors not to place substantial reliance on the forward-looking statements contained in this press release. These statements speak only as of today’s date and Genzyme undertakes no obligation to update or revise the statements.

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