FRAMINGHAM, MA – March 13, 2009 -- GTC Biotherapeutics, Inc. ("GTC", Nasdaq: GTCB) has notified LEO Pharma A/S that GTC is terminating their contract for commercialization and development of ATryn®, GTC’s recombinant form of human antithrombin, in the territories of Europe, Canada and the Middle East. GTC considers LEO to be in breach of its obligations under the contract and is terminating the contract pursuant to its terms and seeking damages under International Chamber of Commerce (ICC) arbitration procedures. GTC has taken this step to provide it a pathway to accelerate and expand progress in Europe, Canada, and the Middle East for both commercialization and further clinical development of ATryn.

“As previously disclosed, LEO indicated last fall that they wished to transfer the program to another partner, and GTC has been working towards achieving this objective while at the same time ensuring that LEO met their contractual obligations,” stated Geoffrey F. Cox, PhD, GTC’s Chairman and CEO. “Despite our best efforts to work with LEO to transfer this program to an alternative partner, this has been a protracted process. GTC strongly believes in the commercial opportunity for ATryn in Europe, Canada and the Middle East in both the approved indication and as a potential treatment for acquired antithrombin deficiency conditions. We have had significant interest in ATryn from a number of potential partners in these territories. We believe that terminating the existing agreement will enable us to progress these discussions in a straightforward manner.”

• Expanding commercial availability of ATryn in Europe. ATryn was approved in 2006 for use throughout the entire EU community in the prophylactic treatment of hereditary antithrombin deficient patients undergoing surgical procedures.
• Expanding the approved indication to include prophylactic treatment of hereditary antithrombin deficient patients undergoing childbirth. Data that had been requested by the European Medicines Agency to consider this additional indication has been available from GTC’s subsequent studies for approval in the United States. GTC had planned for LEO to submit this data to EMEA in the fall of 2008.
• Submitting a request for market authorization with the Canadian health authorities. Data to support this submission has been available from both the EU and US approval packages, and GTC will now be able to move forward with this submission.
• Establishing appropriate health authority approvals and commercialization opportunities in the Middle East.
• Developing ATryn for acquired deficiency indications, including as a potential treatment of disseminated intravascular coagulation, or DIC, associated with severe sepsis. The DIC indication is a large unmet need with over 200,000 patients in Europe and a high mortality rate. GTC believes the market potential exceeds $1 billion per year in the EU. Substantial published data supports the potential efficacy of antithrombin in this indication.

As previously disclosed, LEO Pharma had attempted to terminate its 2005 collaboration agreement with GTC for alleged cause. LEO made it clear that its decision to seek termination was not based on any safety or efficacy issues regarding ATryn, and GTC does not believe that LEO had any basis for such termination. GTC believes it is taking necessary and appropriate steps to protect its legal rights through the arbitration process and the notice of termination. The arbitration process and the consequential matters which follow termination are still in the preliminary stages, and while GTC is confident of its position, it cannot predict likely outcomes or, in the event of any unfavorable outcome, the potential consequences to GTC, including cost.

GTC Biotherapeutics develops, supplies, and commercializes therapeutic proteins produced through transgenic animal technology. ATryn®, GTC’s recombinant human antithrombin, has been approved for use in the United States and Europe. ATryn is the first and only transgenically produced product to be approved for therapeutic use anywhere in the world. In addition to ATryn, 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 being developed for the treatment of hemophilia, and alpha-1 antitrypsin. GTC is developing a monoclonal antibody to CD20 with enhanced ADCC (antibody-dependent cell-mediated cytotoxicity), and a proprietary monoclonal antibody to CD137 with potential indications in oncology and autoimmune disease. GTC is also developing a portfolio of follow-on biologic monoclonal antibodies. 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 potential for expanding the commercial opportunities and indications for ATryn and for further partnering agreements for ATryn in Europe and the prospects for the arbitration process. 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 risks and uncertainties associated with dependence upon the actions of collaboration partners and regulatory agencies and the uncertainties of arbitration. 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.