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Treatment for Antithrombin III Deficiency

Update: ATryn Now FDA Approved - February 6, 2009

BLA Submitted for ATryn

GTC Biotherapeutics Completes BLA Submission For ATryn

FRAMINGHAM, Mass.--(BUSINESS WIRE)--Aug 7, 2008 - GTC Biotherapeutics, Inc. has completed its submission of the final portion of the Biologics License Application, or BLA, for ATryn in the United States. The final portion of the BLA submission includes all of the clinical safety and efficacy data generated from studies of ATryn, including the pivotal study supporting product licensure. ATryn is GTC's recombinant form of human antithrombin, a plasma protein with anticoagulant and anti-inflammatory properties. The BLA requests market authorization for the use of ATryn in 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 patient population.

GTC has requested Priority Review. Priority Review is a procedure the U.S. Food and Drug Administration, or FDA, reserves for products that are intended to treat serious and/or potentially life threatening events and have the potential to fulfill an unmet medical need. ATryn has already been granted Orphan Drug designation, as well as Fast Track status by the FDA. Assuming that Priority Review is granted, GTC anticipates the FDA reaching a decision on the BLA filing in the first quarter of 2009. A definitive agreement has been signed with OVATION Pharmaceuticals, Inc. for commercialization and development rights in the U.S.

ATryn has been approved for use in a similar indication in the European Union. LEO Pharma A/S is marketing ATryn in Europe and is conducting further clinical development.

About GTC Biotherapeutics

GTC Biotherapeutics develops, supplies, and commercializes therapeutic proteins produced through transgenic animal technology. 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 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,

This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, including without limitation statements regarding prospects for Priority Review of the BLA for ATryn and the timing for FDA review and approval of the 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 collaboration partners and 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.


GTC Biotherapeutics, Inc.
Thomas E. Newberry, 508-370-5374
Vice President, Corporate Communications
and Government Relations

Posted: August 2008

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