Myozyme® Receives Positive Opinion from European Regulatory Committee

Proposed Indication Includes All Patients with Pompe Disease.

January 27, 2006, Genzyme Corp. (Nasdaq: GENZ) announced today that the Committee for Human Medicinal Products (CHMP) of the European Medicines Agency has adopted a positive opinion on the marketing authorization application for Myozyme® (alglucosidase alfa). The CHMP unanimously recommended full approval of Myozyme for the treatment of Pompe disease. Marketing authorization by the European Commission is expected within two to three months.

Upon approval, Myozyme will be the first treatment for Pompe disease and one of the first for an inherited muscle disorder. Pompe is a debilitating, progressive and often fatal disease affecting fewer than 10,000 people worldwide.

“This is a hopeful day for Pompe patients and their families and a proud moment for the many people who have worked so hard and met so many challenges to reach this point,” said Henri A. Termeer, chairman and chief executive officer of Genzyme Corp.

The CHMP recommended a broad label for Myozyme. The product indication states: “Myozyme is indicated for long-term enzyme replacement therapy in patients with a confirmed diagnosis of Pompe disease (acid alpha-glucosidase deficiency). The benefits of Myozyme in patients with late-onset Pompe disease have not been established.”

Pompe disease 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. Because of this variability, Pompe disease is generally described as consisting of two forms. In the infantile-onset form, symptoms typically appear within a few months of birth, and babies frequently display a markedly enlarged heart and die within the first year of life. In the late-onset form, symptoms may present anytime during childhood, adolescence or adulthood, and patients experience significant debilitation and premature mortality due to progressive respiratory failure. They often require mechanical ventilation to assist with breathing and wheelchairs to assist with mobility.

The marketing application for Myozyme included clinical data primarily from studies involving patients with infantile-onset Pompe disease. Genzyme initially focused its clinical development program on this population given the urgent medical need. In addition, the company believed it could more rapidly establish Myozyme’s efficacy in this population and thereby make the product available sooner to all patients with Pompe disease. Genzyme recently initiated a clinical trial evaluating the safety and efficacy of Myozyme in patients with late-onset Pompe disease. This trial is designed to provide additional support for Myozyme’s use. Results are expected to be available next year and will be submitted to regulatory authorities.

Ria Broekgaarden, of the Dutch Pompe patient organization VSN (Vereniging Spierziekten Nederland) and secretary of the International Pompe Association, said:

“For patients with Pompe disease, this is a very important moment in history. The CHMP decision represents great hope and progress for all patients with Pompe disease, which in turn will give them a new perspective on their future. Now we must ensure that all patients across Europe will have access to enzyme replacement therapy.”

The CHMP is a scientific body composed of representatives from the 25 member states of the European Union, and Iceland and Norway. The CHMP reviews medical product applications on their scientific and clinical merit and provides advice to the European Commission.

More than 200 patients in 20 countries are currently receiving Myozyme through clinical trials, expanded access programs, or pre-approval regulatory mechanisms.

Genzyme currently manufactures Myozyme at two facilities in the United States. To ensure that it is able to meet the anticipated demand for the product in Europe and throughout the world, the company expects to also produce Myozyme in the future at its new protein manufacturing facility in Geel, Belgium.

About Pompe Disease

Pompe disease is one of more than 40 genetic diseases called lysosomal storage disorders, which are caused by a deficiency or malfunction of specific enzymes found in cell lysosomes. People born with Pompe disease have an inherited deficiency of an enzyme known as acid alpha-glucosidase (GAA). Enzymes, which are protein molecules within cells, trigger biochemical reactions in the body. In a healthy person with normal GAA activity, this particular enzyme would assist in the breakdown of glycogen, a complex sugar molecule stored within a compartment of the cell known as the lysosome. But in Pompe disease, the GAA activity may be dramatically reduced, dysfunctional, or non-existent, resulting in an excessive accumulation of glycogen in the lysosome.

Eventually, the lysosome may become so clogged with glycogen that normal cellular function is disrupted and muscle function is impaired. Although there is glycogen storage in the cells of multiple tissues, heart and skeletal muscles are usually the most seriously affected.

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. This year marks the 25th anniversary of Genzyme’s founding. Since 1981, the company has grown from a small start-up to a diversified enterprise with more than 8,000 employees in locations spanning the globe and 2005 revenues of $2.7 billion. Genzyme has been selected by FORTUNE as one of the “100 Best Companies to Work for” in the United States.

With many established products and services helping patients in more than 80 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 diseases, and diagnostic testing. Genzyme’s commitment to innovation continues today with a substantial development program focused on these fields, as well as heart disease and other areas of unmet medical need.

This press release contains forward-looking statements regarding Myozyme, including the expected timing of E.U. approval, the anticipated timing of the completion of the late-onset trial, and future production plans. These statements are subject to risks and uncertainties that could cause actual results to differ materially from those projected, including that E.U. approval is not received as quickly as expected, that the completion of the late-onset trial is delayed, or that Genzyme encounters manufacturing problems. Please refer to the risks and uncertainties described in reports filed by Genzyme with the Securities and Exchange Commission under the heading “Factors Affecting Future Operating Results” in the Management’s Discussion and Analysis of Financial Condition and Results of Operations section of Genzyme’s Quarterly Report on Form 10-Q for the period ended September 30, 2005 for a more complete discussion of the risks associated with Genzyme’s business. 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 the statements.

Genzyme® and Myozyme® are registered trademarks of Genzyme Corporation. All rights reserved.

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Bo Piela

Media Contact

Genzyme Corp.

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