Genzyme to Reopen Enrollment in Alglucosidase Alfa Temporary Access Program

Date: December 3, 2009

Agreement reached on U.S. approval pathway for Pompe disease treatment

Genzyme Corporation (Nasdaq: GENZ) announced today that it will reopen enrollment in the Alglucosidase Alfa Temporary Access Program (ATAP), a program which provides access to treatment for severely affected adults with Pompe disease prior to commercial approval of Lumizyme™ (alglucosidase alfa). Genzyme and the FDA have also agreed on a path toward approval of Lumizyme.

In November, Genzyme received a Complete Response letter for its Biologic License Application (BLA) for Lumizyme. The company had been seeking approval of Lumizyme produced at a 2000 liter (L) bioreactor scale, manufactured at its Allston plant. In its letter, the FDA stated that satisfactory resolution of deficiencies related to the Allston plant would be required before the Lumizyme application can be approved. Since receiving the Complete Response letter, the company has had several discussions with the FDA on the most expeditious path toward approval. Based on these discussions, Genzyme will now seek approval of the product produced at a larger 4000 L bioreactor scale, in a resubmission to the agency. The 4000 L-scale Lumizyme is produced at Genzyme’s manufacturing plant in Geel, Belgium. Genzyme anticipates that the resubmission will be made this month.

“The reopening of the ATAP program will enable more U.S. patients with Pompe disease access to treatment prior to commercial approval of Lumizyme,” said Genzyme Chairman and Chief Executive Officer Henri A. Termeer. “The U.S. patient community has been very supportive, and we will continue to work closely with the FDA to finalize our efforts and to bring this important therapy to the Pompe community.” The company has provided therapy free of charge to approximately 170 patients since 2007, and will work with the 81 active study sites in the U.S. to enroll additional patients into this program. The ATAP program will remain open until commercial approval of Lumizyme.

Lumizyme (alglucosidase alfa produced at the 4000 L bioreactor scale) is marketed outside of the United States as Myozyme®. Myozyme is commercially approved for the treatment of Pompe disease in over 40 countries worldwide.

About Pompe Disease

Pompe disease is a progressively debilitating disease that manifests as a broad spectrum of clinical symptoms. All patients typically experience progressive muscle weakness and breathing difficulty, but the rate of disease progression can vary widely depending on the age of onset and the extent of organ involvement. When symptoms appear within a few months of birth, babies frequently display a markedly enlarged heart and die within the first year of life. When symptoms appear during childhood, adolescence or adulthood, patients may experience steadily progressive debilitation and premature mortality due to respiratory failure. They often require mechanical ventilation to assist with breathing and wheelchairs to assist with mobility.

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 11,000 employees in locations spanning the globe and 2008 revenues of $4.6 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 approximately 100 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.

This press release contains forward looking statements regarding Genzyme’s future business plans and strategies, including: the potential receipt of FDA approval of Lumizyme produced at the 4000 L bioreactor scale; Genzyme’s regulatory plans, including the expected timing of the resubmission to be made to the FDA for the approval of Lumizyme produced at the 4000 L bioreactor scale; and the expectation that the ATAP program will remain open until commercial approval of Lumizyme. These forward looking statements are subject to risks and uncertainties that may cause actual results to differ materially from those forecasted. These risks and uncertainties include: that Genzyme is unable to file for U.S. approval for the Lumizyme produced using the 4000L process within the expected timeframe for any reason; that Genzyme is unable to obtain FDA approval for Lumizyme produced the 4000L scale; that Genzyme has not forecasted anticipated product demand accurately; that Genzyme is unable to manufacture product in sufficient quantities to meet demand; and the risks and uncertainties described in reports filed by Genzyme with the Securities and Exchange Commission under the Securities Exchange Act of 1934, as amended, including without limitation the information under the heading "Risk Factors" in Genzyme’s Quarterly Report on Form 10-Q for the quarter ending September 30, 2009. Genzyme cautions investors not to place substantial reliance on the forward-looking statements contained in this press release. These statements speak only as of the date of this press release, and Genzyme undertakes no obligation to update or revise these statements.

Genzyme® and Myozyme® are registered trademarks, and Lumizyme™ is a trademark, of Genzyme Corporation or its subsidiaries. All rights reserved.

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