{1} Receives Approval To Market Fabrazyme(R) In Japan

CAMBRIDGE, Mass., Jan. 29 /PRNewswire-FirstCall/ -- Genzyme Corp. announced today that it has received approval to market Fabrazyme(R) (agalsidase beta) in Japan for the treatment of Fabry disease. The company expects to launch Fabrazyme as soon as the Japanese Ministry of Health, Labor and Welfare establishes a local market price for the product.

Genzyme estimates that there are several hundred patients in Japan with Fabry disease. The company completed a study of Fabrazyme in Japan in 2001.

"The approval of Fabrazyme has been eagerly anticipated by many Japanese physicians, Fabry patients and their families," said Yoshikatsu Eto, M.D., professor and chairman of the Department of Pediatrics at the Tokyo Jikei University School of Medicine and principal investigator for Genzyme's study of Fabrazyme in Japan.

Genzyme has a well-established sales and marketing organization in Japan, where the company has operated for more than 15 years. Genzyme has marketed an enzyme replacement therapy for Gaucher disease in Japan since 1996, enabling the company to develop a close relationship with physicians who specialize in the treatment of genetic disorders.

"We are pleased to bring this therapy to patients who suffer from this serious and life-threatening disease," said Sandford D. Smith, president of Genzyme's international group. "We anticipate that Fabrazyme will be adopted quickly by physicians who are caring for Fabry patients at multiple centers in Japan."

Fabry disease is a genetic disorder caused by an enzyme deficiency. The disease causes certain fats to accumulate in the blood vessels over many years, leading to the involvement of various tissues and organs in the body, including the kidneys and heart, which can result in organ failure and stroke. People with Fabry disease often must cope with significant pain and disability and typically have a shortened life span. The disease affects approximately 5,000 people worldwide.

About Fabrazyme

In more than 30 countries, Fabrazyme is indicated for the treatment of Fabry disease, with a recommended dose of 1 mg/kg of body weight administered once every 2 weeks as an intravenous infusion. In the United States, where this press release has been issued, the product label states that "Fabrazyme is indicated for use in patients with Fabry disease. Fabrazyme reduces globotriaoscylceramide (GL-3) deposition in capillary endothelium of the kidney and certain other cell types." The reduction of GL-3 inclusions suggests that Fabrazyme may ameliorate disease expression; however, the relationship of GL-3 inclusion reduction to specific clinical manifestations of Fabry disease has not been established.

The most serious and common side effects reported with Fabrazyme are infusion reactions. Infusion reactions may include: increase in heart rate, increase in blood pressure up to a few hours after infusion, throat tightness, chest pain/tightness, shortness of breath, fever, chills, abdominal pain, itching, hives, nausea, vomiting, lip or ear swelling, rash, decrease in blood pressure, muscle pain, and headache. Infusion reactions occurred in many patients treated with Fabrazyme, and some of the reactions were severe. Anti- fever medications (for example, acetaminophen or ibuprofen) should be administered prior to infusion to reduce the potential for an infusion reaction. Infusion reactions occurred in some patients after receiving anti- fever medications, antihistamines and oral steroids. Because of the potential for severe infusion reactions, appropriate medical support measures should be readily available when Fabrazyme is administered.

About Genzyme

Genzyme Corporation is a global biotechnology company dedicated to making a major positive impact on the lives of people with serious diseases. The company's broad product portfolio is focused on rare genetic disorders, renal disease, osteoarthritis and immune-mediated diseases, and includes an industry-leading array of diagnostic products and services. Genzyme's commitment to innovation continues today with research into novel approaches to cancer, heart disease, and other areas of unmet medical need. More than 5,300 Genzyme employees in offices around the globe serve patients in over 80 countries.

This press release contains forward-looking statements, including statements regarding: the anticipated timing of market launch of Fabrazyme in Japan; estimates of the Fabry patient population in Japan and worldwide; and expectations concerning the adoption of Fabrazyme by physicians in Japan. These statements are subject to risks and uncertainties that could cause actual results to differ materially from those projected in these forward- looking statements. These risks and uncertainties include, among others: the timing of the decision by the Japanese Ministry of Health, Labor and Welfare concerning the reimbursement price for Fabrazyme; market acceptance of Fabrazyme in Japan; decisions made by physicians and patients concerning the use of Fabrazyme and the actual rate of adoption; the effectiveness of Genzyme's sales and marketing organization; the accuracy of Genzyme's information concerning the Fabry patient population; and the factors discussed in Genzyme's periodic reports filed with the United States Securities Exchange Commission, including under the caption "Factors Affecting Future Operating Results" in Genzyme's Quarterly Report on Form 10-Q for the period ended September 30, 2003. We caution investors not to place undue reliance on the forward-looking statements contained in this press release. These statements speak only as of the date of this document and we undertake no obligation to update or revise the statements.

Genzyme's press releases and other company information are available at http://www.genzyme.com/ and by calling Genzyme's investor information line at 1-800- 905-4369 within the United States or 1-703-797-1866 outside the United States.

Media Contact: Bo Piela (617) 768-6579 Investor Contact: Sally Curley (617) 768-6140

Genzyme Corp.