Genzyme Announces Data from First Phase 3 Study of Tolevamer in Patients with C. difficile Associated Diarrhea Genzyme Corp. announced top-line data today from the first of two Phase 3 clinical studies to assess the safety and efficacy of tolevamer liquid, an investigational, non-antibiotic, polymer therapy for patients with Clostridium difficile associated diarrhea (CDAD). The second Phase 3 study of tolevamer liquid is fully enrolled and results are expected later this year. In this first Phase 3 study known as the Polymer Alternative for CDAD Treatment (PACT) study, tolevamer liquid did not meet its primary endpoint of non-inferiority to the standard prescribed oral dose of the antibiotic vancomycin, as measured by the percent of patients with resolution of CDAD. This result contrasts with the findings from Genzymeâ€™s earlier Phase 2 study of a solid oral dosage formulation of tolevamer that met its primary endpoint of non-inferiority compared to vancomycin. Consistent with recent published studies, high rates of CDAD recurrences were observed in patients treated with either vancomycin or metronidazole. High CDAD recurrence rates were not observed in patients treated with tolevamer liquid. Tolevamer liquid was generally well tolerated with no unanticipated safety concerns. Data from this first Phase 3 study is expected to be presented at a future medical conference. â€œThese are disappointing results that alter our expectations about the potential for commercializing tolevamer in the near future,â€ stated Henri A. Termeer, chairman and chief executive officer of Genzyme Corp. â€œThe results of our second Phase 3 study will be available later this year and will help us determine what contribution tolevamer might be able to make in addressing this serious unmet medical need.â€ C. difficile has become one of the most significant infection control concerns in healthcare today. Physicians worldwide are confronting a worsening epidemic, with an alarming rise in the incidence of disease, higher numbers of patients with complications and more frequent failures of standard antibiotic therapy. Tolevamer is designed to bind and neutralize the toxins released by C. difficile that damage the intestine. A non-antibiotic approach has the potential to treat CDAD and reduce the number of disease recurrences, resulting in improved quality of life for the patient and significant savings to the healthcare system. About the PACT Study The PACT study, which involved more than 1,100 patients at approximately 300 sites in North America, Europe, and Australia, is the largest of its kind ever to be conducted for CDAD. In this trial, tolevamer was compared to metronidazole and vancomycin. Aside from testing tolevamerâ€™s efficacy, this was also the first large, rigorously designed, multi-center clinical study that will compare the efficacy of the current standards of care. About Clostridium difficile C. difficile proliferates in the setting of altered normal colonic bacterial flora, most commonly due to the administration of broad-spectrum antibiotics. Once established in the colon, C. difficile produces toxins that disrupt the intestinal lining, causing cell death and inflammation that result in diarrhea and colitis. Earlier studies have shown that even after successful treatment with the current standard of care, approximately 20 percent of patients experience a recurrence of CDAD potentially requiring repeat hospitalization. In addition, a subset of patients with CDAD develop multiple recurrences of the disease, with symptoms that may persist for years. 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 9,000 employees in locations spanning the globe and 2006 revenues of $3.2 billion. Genzyme has been selected by FORTUNE as one of the â€œ100 Best Companies to Work forâ€ 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. This press release contains forward-looking statements, including statements regarding the potential for commercializing tolevamer in the future, when data from this Phase 3 study of tolevamer will be presented and when the results of the second Phase 3 study of tolevamer will be available. 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 actual safety and efficacy of tolevamer; the outcome of discussions with regulatory authorities regarding clinical studies and the approval of tolevamer for CDAD and the timing of such discussions; additional analysis of the data from the first Phase 3 study; the results of the second Phase 3 study and whether such results are consistent with this data; the timing of the second Phase 3 study; 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 "Risk Factors" 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 ending March 31, 2007. 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.