Genzyme Files for Approval of Sevelamer Carbonate for Patients on Dialysis

December 21, 2006 - Genzyme Corp. (Nasdaq: GENZ) announced today that it has filed a New Drug Application (NDA) with the U.S. Food and Drug Administration seeking approval of sevelamer carbonate for the control of serum phosphorus in patients with chronic kidney disease on dialysis. Sevelamer carbonate will be marketed under the trade name RenvelaTM (ren-VEL-uh).

Renvela is being developed as a next generation phosphate binder to replace Renagel® (sevelamer hydrochloride), the most-prescribed phosphate binder in the United States. Genzyme is seeking approval for use of Renvela in patients with chronic kidney disease (CKD) on dialysis. Like Renagel, Renvela is a non-calcium, non-metal, non-absorbed phosphate binder and will be available in 800mg tablets.

“Submission of this NDA marks an important milestone as we prepare to introduce our next generation of sevelamer,” said John P. Butler, president, Genzyme Renal. “Development of this therapy demonstrates our commitment to meeting the needs of all patients who can benefit from using sevelamer.”

In addition to today’s filing, Genzyme is advancing a clinical program investigating the use of Renvela for hyperphosphatemic patients with chronic kidney disease who have not progressed to dialysis. Enrollment has been completed in the study evaluating Renvela for this indication.

Enrollment is also complete in a study comparing a powder form of sevelamer carbonate dosed once a day to Renagel tablets dosed three times a day. Development of a powder form of the product would offer a more convenient option for patients, thereby improving compliance.

About Renagel

Renagel controls serum phosphorus in patients with CKD on hemodialysis. Controlling serum phosphorus is an important element in the care of hemodialysis patients. Elevated serum phosphorus levels are common in dialysis patients and associated with increased risk of cardiovascular mortality. Renagel provides the added benefit of significant LDL cholesterol reduction (32 percent).

The National Kidney Foundation’s 2003 K/DOQI guidelines for Bone Metabolism and Disease in Chronic Kidney Disease recommend sevelamer hydrochloride as a first-line treatment option to control phosphorus. Renagel is the only phosphate binder available that does not contain either calcium or a metal. It has an established safety profile, is not systemically absorbed and provides phosphorus control without the concerns of calcium or metal accumulation. Renagel is used by more than 350,000 people worldwide

Product Information

Renagel is indicated for the control of serum phosphorus in patients with chronic kidney disease (CKD) on hemodialysis. Renagel is contraindicated in patients with hypophosphatemia or bowel obstruction. In a 52-week study, the most common side effects included vomiting, nausea, diarrhea, and dyspepsia. Drug-drug interactions may occur with some medications and should be taken into consideration when instructing patients how to take Renagel.

For more information about Renagel, including complete prescribing information, please visit www.renagel.com.

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 8,500 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, without limitation, statements about: potential uses and benefits of, and indications for, Renvela; the potential approval of Renvela; plans for new indications, formulations and dosing regimens; and plans to continue the clinical development program. 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 discussions with the FDA regarding the approval of Renvela; the timing and content of decisions by the FDA relating to the approval of Renvela; the actual efficacy and safety of Renvela; the actual timing and results of clinical trials; further analysis of clinical trial data; 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 in Genzyme’s Quarterly Report on Form 10-Q for the period ended September 30, 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 these statements.

Genzyme® and Renagel® are registered trademarks and RenvelaTM is a trademark of Genzyme Corporation. All rights reserved.

Contact Information

Bo Piela

Media Contact

Genzyme Corp.

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