Date: January 17, 2006

Genzyme Corp. (Nasdaq: GENZ) announced today that the Food and Drug Administration has extended by 90 days the review period for the biologics license application for Myozyme® (alglucosidase alfa). The new action date for the application is April 28, 2006. The purpose of the extension is to provide the FDA with sufficient time to review additional information submitted by Genzyme in late December at the agency’s request


“This is a brief extension of the review period, and we continue to expect that Myozyme will be approved in the United States during the first half of this year,” said Alison Lawton, Genzyme’s senior vice president for regulatory affairs. “We have worked closely with the FDA throughout the review process and are confident the agency recognizes the urgency of making this treatment available to patients.”

Myozyme has been developed for the treatment of Pompe disease, a debilitating, progressive and often fatal muscular disorder. Genzyme submitted a biologics license application for Myozyme in late July. The application was given Priority Review status, which required the FDA to act within six months.

Genzyme is currently engaged in a broad range of activities to prepare for Myozyme’s introduction in the United States and in Europe, where the Committee for Human Medicinal Products is expected to issue an opinion later this month on the marketing authorization application for Myozyme.

Approximately 200 patients in 14 countries are currently receiving Myozyme through clinical trials, expanded access programs, or pre-approval regulatory mechanisms.

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 the expected timing of U.S. and European regulatory action on Myozyme.

These statements are subject to risks and uncertainties that could cause actual results to differ materially from those projected.

These risks and uncertainties include that the FDA may not approve Myozyme on the timeframe anticipated by Genzyme or at all.

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 ending 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 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.