Genzyme Launches Colorectal Cancer Test To Determine Appropriate Camptosar® Dosage

Preferred Partnership With Third Wave Advances Personalized Medicine

December 6, 2005, Genzyme Corporation (Nasdaq: GENZ) today announced the launch of the Invader® UGT1A1 Molecular Assay for colorectal cancer patients in the North American market who are being considered for, or currently taking, the chemotherapy Camptosar® (irinotecan). The test was recently cleared by the U.S. Food and Drug Administration (FDA) and was developed by Third Wave Technologies Inc. (Nasdaq: TWTI). Third Wave has designated Genzyme as its preferred laboratory partner for marketing UGT1A1 in the United States.

The UGT1A1 Molecular Assay identifies patients who may be at increased risk for severe adverse reactions to Camptosar by detecting variations in the UGT1A1 gene that have been associated with that risk. A prospective clinical study indicated that patients with one of these variations have a greater than nine-fold risk of experiencing increased white blood cell counts from Camptosar than patients without it. Camptosar labeling was recently updated to include dosing recommendations based on a patient’s UGT1A1 status. Approximately 150,000 new cases of colorectal cancer are diagnosed each year in the United States, 40 to 50 percent of which are metastatic.

“The UGT1A1 Molecular Invader Assay is a significant addition to Genzyme’s oncology testing menu. We have initiated an education program aimed at physicians because it is critical that they are aware that this test will help them understand their patients’ risk of serious side effects. This will help doctors treat their colorectal cancer patients with the appropriate dose of Camptosar,” said Mara Aspinall, president of Genzyme Genetics, a business unit of Genzyme Corporation that focuses on the research and development of high quality, complex testing services.

“We are very pleased that Genzyme will make this test widely available in the United States and we believe that it will play an important role in patients’ course of treatment,” said John J. Puisis, president and chief executive officer of Third Wave.

The UGT1A1 test is built on the accuracy, scalability and ease of use of Third Wave’s unique, patented Invader® chemistry. In a study submitted to the FDA as part of the company’s clearance application, the Invader® UGT1A1 test was 100 percent accurate compared to DNA sequencing, the standard for genotype determination.1

Third Wave selected Genzyme as its preferred laboratory partner because of Genzyme’s demonstrated commitment to developing, marketing and selling personalized tests for cancer therapies. Genzyme Genetics has launched several major new cancer tests this year, all of which help to identify patients likely to respond to targeted cancer therapies. Most recently, Genzyme Genetics announced that it entered into a license agreement with the University of California at Los Angeles Jonsson Cancer Center to obtain exclusive, worldwide diagnostic rights to its discovery of gene mutations believed to be associated with resistance to Gleevec® (imatinib mesylate), the current first-line therapy for patients with chronic myeloid leukemia.

1n=285; 95% lower limit confidence=99%

About Colorectal Cancer

Colorectal cancer refers to cancer that starts in the colon or rectum. It is the third most common cancer found in men and women and the second leading cause of cancer-related deaths in the United States. The American Cancer Society estimates that there will be about 104,950 new cases of colon cancer and 40,340 new cases of rectal cancer diagnosed in 2005. There are approximately 1 million survivors of colorectal cancer in the United States today, due largely to earlier detection and improved treatment options.

About Genzyme Genetics

Genzyme Genetics is a leading, nationwide provider of high-quality, complex diagnostic 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. Founded in 1981, Genzyme has grown from a small start-up to a diversified enterprise with more than 8,000 employees in locations spanning the globe and 2004 revenues of $2.2 billion. 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.

About Third Wave Technologies

Third Wave Technologies is a leader in the development and marketing of molecular diagnostics for a variety of DNA and RNA analysis applications, providing physicians and researchers with superior tools to diagnose and treat disease. Third Wave’s Invader® chemistry provides the company’s customers with exceptional performance, scalability, and ease of use. The company offers a number of clinical products based on its Invader® chemistry for genetic testing related to multiple disease areas. For more information about Third Wave and its products, please visit the company’s website at www.twt.com.

This press release contains forward looking statements about the number of new colorectal cancer cases and Genzyme’s business and strategy, including statements about the Invader UGT1A1 Molecular Assay and its expected benefits for colorectal cancer patients, such as the avoidance of certain side effects and improvements in treatments, and the launch, marketing and sale of the UGT1A1 test by Genzyme Genetics. 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, medical advances which may reduce the number of new colorectal cancer cases, scientific, technical and manufacturing issues that could prevent the U.S. marketing and availability of the Invader Assay as contemplated, the failure of the Invader Assay to produce diagnostic results as anticipated, the commercial acceptance of the Invader Assay, including the acceptance of the test 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 quarter ended September 30, 2005. The statements in this press release speak only as of the date of this release. Genzyme cautions investors not to place substantial reliance on the forward-looking statements contained in this press release.

Genzyme® is a registered trademark of Genzyme Corporation. Invader® is a registered trademark of Third Wave Technologies, Inc. Camptosar® is a registered trademark of Pfizer. Gleevec® is a registered trademark of Novartis. All rights reserved.

Contact Information

Erin Emlock

Public Relations Specialist

Genzyme Corporation

Contact via E-mail