Genzyme Announces FDA Approval of Thyrogen^® For Use In Thyroid Cancer Ablation

Date: December 17, 2007

Genzyme Corp. (Nasdaq: GENZ) announced today that the U.S. Food and Drug Administration (FDA) has approved a supplemental indication for Thyrogen^® (thyrotropin alfa for injection) to be used in combination with radioiodine to ablate, or destroy, the remaining thyroid tissue in patients who have had their cancerous thyroids removed. Remnant ablation is a procedure that patients commonly undergo when being treated for thyroid cancer.

"This new indication extends the significant benefits of Thyrogen to patients during their initial treatment for thyroid cancer, in addition to its current use in follow-up diagnostic procedures to detect recurrence," said Mike Heslop, senior vice president and general manager of Genzyme's endocrine business. "This is an important milestone in our ongoing effort to expand the clinical applications of Thyrogen to improve patient care."

The American Cancer Society estimates that in 2007, about 33,550 new cases of thyroid cancer will be diagnosed in the United States. Approximately 90 percent of all thyroid cancers are well-differentiated, making those patients candidates for the remnant ablation procedure.

"The development of new treatment options for thyroid cancer patients is critical, as this disease has the fastest rising incidence of all cancers among women in the U.S.," said clinical investigator Paul Ladenson, M.D., professor and director of endocrinology at The Johns Hopkins University School of Medicine. "The availability of Thyrogen for use in remnant ablation is a notable advance, as it permits patients to maintain a good quality of life during the course of their thyroid cancer treatment and follow-up testing."

Thyrogen was initially approved in the U.S. in 1998 and Europe in 2001 for use as a diagnostic tool in the management of patients being tested for the recurrence of well-differentiated thyroid cancer. The product helps increase the sensitivity of testing while allowing patients to avoid the potentially debilitating symptoms of thyroid hormone withdrawal. Genzyme received additional European approval for Thyrogen's use during remnant ablation procedures in 2005.

Thyrogen Use in Ablation

The new indication allows Thyrogen to be used in conjunction with radioiodine for the most common approach to treating thyroid cancer. This includes surgical removal of the cancerous thyroid followed by remnant ablation, which destroys any remaining thyroid tissue. This can help reduce the risk of disease recurrence and facilitate follow-up monitoring.

In remnant ablation, patients take a drink or a capsule that contains radioactive iodine, which is taken up by any remaining thyroid cells. To enhance the uptake of radioiodine, the level of thyroid stimulating hormone (TSH) in a patient's bloodstream must be enhanced. Patients currently stop taking thyroid hormone supplements to elevate TSH levels. Doing so, however, often causes side effects associated with hypothyroidism, which may include fatigue, difficulty concentrating, short-term memory impairment and depression. Thyrogen is a recombinant form of TSH that is administered by injection, allowing patients to continue taking hormone supplements and avoid the symptoms associated with hormone withdrawal.

The FDA approved Thyrogen for remnant ablation based on results from a pivotal clinical study which suggest that treatment with Thyrogen is similar to withdrawal from thyroid hormone in achieving ablation, and that it could significantly reduce the side effects of thyroid hormone withdrawal by allowing patients to remain on hormone replacement therapy.

Most cases of thyroid cancer are discovered during a routine physical examination when a painless lump is found in the thyroid. It is three times more common in women than in men. Although well-differentiated thyroid cancer is very treatable, ongoing monitoring is important as the disease can recur in up to 30 percent of patients.

About Thyrogen

Thyrogen is currently available in more than 45 countries. It was first approved in the United States in 1998 for use in patients with well-differentiated thyroid cancer who have had their thyroid removed as an adjunctive diagnostic tool for serum thyroglobulin testing with or without radioiodine imaging. These patients must take thyroid hormone supplements and undergo periodic testing for recurrent or metastatic cancer. Thyrogen allows patients to remain on their hormone supplements during this testing and avoid the debilitating symptoms of clinical hypothyroidism.

With the new approval, Thyrogen may also be used as an adjunctive treatment for radioiodine ablation of thyroid tissue remnants in patients with well-differentiated thyroid cancer who have recently had their thyroid removed and who do not have evidence of metastatic thyroid cancer.

Thyrogen is injected in a muscle, and is available only by prescription. The most common side effects reported in clinical studies were nausea, headache, fatigue, vomiting and dizziness. When using Thyrogen as a diagnostic tool, there is a risk that thyroid cancer cells may not be detected and diagnosis of recurring cancer may be missed. Please see full prescribing information at www.thyrogen.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. Since 1981, the company has grown from a small start-up to a diversified enterprise with more than 9,500 employees in locations spanning the globe and 2006 revenues of $3.2 billion. In 2007, Genzyme was chosen to receive the National Medal of Technology, the highest honor awarded by the President of the United States for technological innovation. In 2006 and 2007, Genzyme was 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 nearly 90 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 diagnostic testing. Genzyme's commitment to innovation continues today with a substantial development program focused on these fields, as well as immune disease, infectious disease, and other areas of unmet medical need.

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