October 6, 2008

FDA Accepts ATryn(R) BLA Filing

The US Food and Drug Administration, or FDA, has accepted for review GTC Biotherapeutics, Inc.'s ("GTC", Nasdaq: GTCB) Biologics License Application, or BLA, for ATryn(R). FDA's Blood Products Advisory Committee intends to review the BLA for ATryn(R) during a meeting that is being planned for January 2009. Based on the achievement of these milestones, GTC has received $2 million in additional milestone payments from OVATION Pharmaceuticals, Inc.

As previously announced, ATryn(R) has been designated an Orphan Drug and FDA has determined that the product fulfills the criteria for Fast Track status. The ATryn(R) BLA will also receive Priority Review. Priority Review is granted to only to those products that, if approved, would provide a significant improvement in the safety or effectiveness of the treatment, diagnosis or prevention of a serious or life-threatening disease. Under Priority Review, the target date for FDA action on the BLA is February 7, 2009. This action date was affirmed by the FDA following preliminary review of the BLA performed in accepting the BLA.

ATryn(R) is GTC's recombinant form of human antithrombin, a plasma protein with anticoagulant and anti-inflammatory properties. The company seeks regulatory approval of ATryn(R) in the United States for the prophylactic treatment of deep vein thrombosis and other thromboembolisms in patients with hereditary antithrombin deficiency who are undergoing high risk surgical and childbirth procedures. There are no other recombinant forms of antithrombin available to treat this rare patient population. GTC has licensed ATryn(R) to OVATION Pharmaceuticals, Inc. to develop and market it in the United States.

About GTC Biotherapeutics

GTC Biotherapeutics develops, supplies, and commercializes therapeutic proteins produced through transgenic animal technology. In addition to ATryn(R), GTC is developing a portfolio of recombinant human plasma proteins with known therapeutic properties. These proteins include recombinant forms of human coagulation factors VIIa, VIII, and IX, which are used for the treatment of hemophilia, and alpha-1 antitrypsin. GTC also has a monoclonal antibody portfolio that includes a monoclonal antibody to CD20 and a monoclonal antibody to CD137. 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 proteins 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 the Advisory Committee meeting and target action dates for the ATryn(R) 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 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.