Product is First Treatment for Pompe Disease

Genzyme Corp. (Nasdaq: GENZ) announced today that it has received marketing authorization for Myozyme® (alglucosidase alfa) in the European Union. Myozyme has been approved for long-term enzyme replacement therapy in patients with a confirmed diagnosis of Pompe disease, a debilitating, progressive and often fatal disorder affecting fewer than 10,000 people worldwide. The product is the first treatment ever approved for Pompe disease and one of the first for an inherited muscle disorder.

“This is an extraordinary moment for Pompe patients and their families,” said Henri A. Termeer, chairman and chief executive officer of Genzyme Corp. “The effort to develop Myozyme has required the enormous commitment of many people throughout Genzyme and across the Pompe community, who have worked with a great sense of urgency and have overcome tremendous challenges. Our focus now is to ensure that Myozyme is available to all patients who need treatment.”

Myozyme has received orphan medicinal product designation in Europe. The orphan medicinal products regulation is designed to encourage the development of treatments for rare disorders such as Pompe disease, for which no therapies have existed previously. Genzyme will introduce Myozyme in Europe on a country-by-country basis, as pricing and reimbursement approvals are obtained.

Ria Broekgaarden, of the Dutch Pompe patient organization VSN (Vereniging Spierziekten Nederland) and secretary of the International Pompe Association, said, “For people with Pompe disease, this is a very important moment in history. The approval of this treatment represents great hope and progress for all Pompe patients, which in turn will give them a new perspective on their future.”

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. 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.

Genzyme began working to develop a treatment for Pompe disease in 1998. In 2003, the company initiated clinical studies of Myozyme, which produced highly encouraging results and formed the basis of the company’s regulatory submissions. In the pivotal clinical study, 83 percent of patients treated with Myozyme were both alive and free of invasive ventilator support at 18 months of age, compared with two percent of patients in the historical cohort. The trial, which met its primary endpoint, enrolled 18 patients with infantile-onset Pompe disease, who began receiving therapy at approximately six months of age. Approximately 39 percent of patients treated with Myozyme developed infusion associated reactions, which were mostly mild to moderate in nature. Two patients experienced serious infusion reactions. One experienced urticaria, the other experienced urticaria, rales, tachycardia, decreased oxygen saturation, bronchospasm, tachypnea, periorbital edema and hypertension.

Genzyme recently completed enrollment in its clinical trial involving patients with late-onset Pompe disease. Ninety patients are participating in this international, placebo-controlled study. Currently, more than 270 patients in 30 countries are receiving Myozyme through clinical trials, expanded access programs, or pre-approval regulatory mechanisms.

Genzyme 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, and its new fill/finish facility in Waterford, Ireland.

About Pompe Disease

Pompe disease, also known as Acid Maltase Deficiency or Glycogen Storage Disease Type II, 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.

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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 a forward-looking statement regarding Myozyme manufacturing. This statement is subject to risks and uncertainties that could cause actual results to differ materially from those projected, including that Genzyme is unable to produce Myozyme at its Geel, Belgium facility or produce it in sufficient quantities to meet demand. 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 Annual Report on Form 10-K for the year ended December 31, 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 statement contained in this press release. This statement speaks only as of the date of this press release, and Genzyme undertakes no obligation to update or revise the statement.

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