PRESS RELEASE: GTC Obtains FDA Fast Track Designation for ATryn

GTC Obtains FDA Fast Track Designation for ATryn and Permission to Submit a Rolling BLA

FRAMINGHAM, Mass. -- GTC Biotherapeutics announced today that the US Food and Drug Administration, or FDA, has designated ATryn® a “fast track product” entitled to accelerated FDA review for the hereditary antithrombin deficiency indication. The FDA has also granted GTC permission to submit the associated Biologics License Application, or BLA, for ATryn® on a rolling basis. Fast track designation is provided to those products that are intended to treat serious or potentially life threatening conditions for which there is an unmet medical need. The BLA requesting marketing approval for ATryn® will be submitted as sections are completed rather than waiting for all sections to be submitted together, enabling FDA review to begin sooner. GTC anticipates filing the initial sections with the FDA in the fourth quarter and completing the rolling submission after all clinical data is gathered, analyzed, and available for the BLA, which is planned to be by the end of the first quarter of 2008.

ATryn® is GTC’s recombinant form of human antithrombin, a protein with anticoagulant and anti-inflammatory properties that is normally present in human plasma. ATryn® is being investigated in a Phase III comparative study for the treatment of hereditary antithrombin deficiency, or HD, patients at risk for developing deep vein thrombosis or thromboembolism while undergoing surgical procedures or childbirth. Top line data from this study is planned to be available late in the fourth quarter.

ATryn® is produced in the milk of goats that have incorporated the human antithrombin gene such that it is only expressed during lactation. This technology enables an alternative supply of antithrombin that is unconstrained by the limited availability of plasma-sourced material.

ATryn® has been approved for use in the European Union for the treatment of HD patients undergoing surgical procedures, marking the first time that any transgenically produced therapeutic protein had been approved anywhere in the world. LEO Pharma A/S, GTC’s commercial and development partner in Europe, Canada and the Middle East, has initiated a Phase II study of ATryn® in the treatment of patients with disseminated intravascular coagulation, or DIC, associated with severe sepsis. DIC is a large unmet medical with approximately 500,000 patients in the US and EU each year and up to 50% mortality.

About GTC Biotherapeutics

GTC Biotherapeutics develops, produces, and commercializes therapeutic proteins through transgenic animal technology. In addition to ATryn®, GTC is working with LFB Biotechnologies to develop recombinant forms of human factor VIIa and a CD20 monoclonal antibody. GTC’s intellectual property includes a patent in the United States through 2021 for the production of any therapeutic protein in the milk of any transgenic mammal. GTC’s transgenic production platform is particularly well suited to enabling cost effective development of proteins that are difficult to express in traditional recombinant production systems as well as those that are required in large volumes. Additional information is available on the GTC web site, http://www.gtc-bio.com.

This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, including without limitation statements regarding the timing of completion of GTC’s current Phase III study of ATryn® and filing of the associated BLA. Such forward-looking statements are subject to a number of risks, uncertainties and other factors that could cause actual results to differ materially from future results expressed or implied by such statements. Factors that may cause such differences include, but are not limited to, the risks and uncertainties discussed in GTC's most recent Annual Report on Form 10-K and its other periodic reports filed with the Securities and Exchange Commission, including the uncertainties associated with conducting clinical studies, and the risks and uncertainties associated with dependence upon the actions of regulatory agencies. GTC cautions investors not to place undue reliance on the forward-looking statements contained in this release. These statements speak only as of the date of this document, and GTC undertakes no obligation to update or revise the statements, except as may be required by law.