Genzyme Corporation (Nasdaq: GENZ) announced today the availability of two new molecular tests for acute myelogenous leukemia (AML) with the launch of FLT3 Mutation Analysis and WT1 RQ-PCR. FLT3 mutations are considered a prognostic indicator of poor survival and response to standard chemotherapies. The WT1 RQ PCR test allows physicians to monitor AML patients for early relapse during and following therapy. Together, these tests may enable oncologists to better manage their patients.

"Understanding an AML patient's prognosis will allow the physician and patient to make more effective treatment decisions. We are very pleased to expand our testing menu and to increase the information available to the treating physician," said Mara Aspinall, president of Genzyme Genetics, the business unit of Genzyme Corp. focused on the research, development and provision of high quality, complex testing services. "These innovative tests highlight the increasing importance and value of personalized medicine in oncology."

FLT3 receptor mutations are one of the most common genetic abnormalities in AML and have been shown to be an independent predictor of survival. Approximately 30 percent of patients with AML have FLT3 mutations.

Genzyme's exclusive WT1 RQ-PCR test is designed to detect minimal residual disease (MRD), or very low levels of disease. The WT1 gene is expressed in approximately 90 percent of patients with AML. Use of this test enables physicians to identify AML patients at high risk for relapse weeks to months prior to recurrence. The WT1 test is designed to provide oncologists additional information and time to implement other treatment strategies.

"The FLT3 and WT1 tests may have the potential to change the current paradigms of AML therapy. The results of these tests could influence treatment strategies," said Morton Coleman, M.D., professor of Medical Oncology and Hematology, Weill Medical College of Cornell University.

About Acute Myelogenous Leukemia

According to the American Cancer Society, AML is a type of cancer that starts in blood-forming cells of the bone marrow and then invades the blood. It can spread to the lymph nodes, spleen, liver, and other parts of the body. In 2006, there will be approximately 12,000 new cases of AML, 90 percent of which will be diagnosed in adults. The average age of a patient with AML is 65.

While advances in the treatment of AML have resulted in substantially improved remission rates, with 60 to 70 percent of adults achieving a complete response, more than 50 percent of these patients will relapse and their long-term survival is less than 40 percent.

About Genzyme Genetics

Genzyme Genetics is a leading, nationwide provider of high-quality, complex testing services for physicians and their patients. With CLIA-certified laboratories and counseling facilities located across the U.S., Genzyme Genetics offers extensive diagnostic testing services, supported by innovative technology and a commitment to quality service and trusted information. Genzyme Genetics is a business unit of Genzyme Corporation.

About Genzyme Corporation

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, including the statements regarding improvements in the effectiveness of treatment of patients with AML, the ability of the WT1 test to identify patients at high risk of relapse and the potential creation of a paradigm shift in AML therapy. 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 failure of the FLT3 and WT1 tests to produce diagnostic results as anticipated, and the commercial acceptance of the FLT3 and WT1 tests, including the acceptance of the tests at price levels that are economically viable for Genzyme Genetics, 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 "Factors Affecting Future Operating Results" in the Management's Discussion and Analysis of Financial Condition and Results of Operations section of the Genzyme Quarterly Report on Form 10-Q for the period ending March 31, 2006. 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.

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