GTC Biotherapeutics and USAMRIID to Cooperatively Study ATryn for Viral Hemorrhagic Diseases.

FRAMINGHAM, Mass. -- GTC Biotherapeutics, Inc. ("GTC", Nasdaq: GTCB) announced today that it has signed a two-year cooperative research and development agreement (CRADA) with the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) to evaluate the potential therapeutic application of ATryn(R) to hemorrhagic diseases resulting from infections of the Ebola and Marburg viruses. Under the CRADA, GTC will supply ATryn(R), its recombinant form of human antithrombin, for in vitro and preclinical studies developed by the USAMRIID. USAMRIID will perform all work associated with the live viruses.

"We believe that ATryn(R) has broad therapeutic potential in situations where antithrombin deficiency may be part of the progression of the disease," stated Geoffrey F. Cox, Ph.D., GTC's Chairman and Chief Executive Officer. "This CRADA allows for further evaluation of ATryn(R)'s therapeutic potential while GTC continues in discussions with potential commercial development partners."

ATryn(R)

ATryn(R) is a recombinant form of human antithrombin, a plasma protein with anticoagulant and anti-inflammatory properties. GTC expresses this protein in the milk of goats that have the human antithrombin gene linked to a milk-protein promoter. This transgenic approach provides the opportunity to produce recombinant forms of proteins, such as antithrombin, that are difficult to express in conventional production methods.

The European Medicines Agency (EMEA) is reviewing a Marketing Authorization Application (MAA) for the use of ATryn(R) in the prophylactic treatment of patients with hereditary antithrombin deficiency (HD) during high-risk situations such as surgery and childbirth. Subject to satisfactory approval of the MAA, GTC is planning for a European market launch of ATryn(R) in mid-2005.

Hemorrhagic Diseases

Infections with Ebola or Marburg viruses (EBOV or MARV), both classified as bioterrorism agents, cause devastating illnesses, including hemorrhagic fever. Although there have been reports of recent successes with candidate vaccines and post-exposure therapeutics, there are currently no approved treatment strategies for these viruses. This collaboration would allow for the evaluation of a novel intervention strategy using ATryn(R) to target an important aspect of the disease pathogenesis, i.e., the development of coagulation abnormalities. ATryn(R), due to its transgenic production platform, also offers cost-effective manufacturing and stockpiling of the amounts necessary to provide protection for large populations in case of emergency should an evaluation indicate that there is significant potential as a treatment option.

Acute mortality caused by the Zaire species of EBOV has been about 80% in outbreaks in humans and nearly 100% in monkey models of the genus Macaca. The pathogenesis of EBOV and MARV hemorrhagic fevers is not completely understood. The disease triggered in primates is thought to involve inappropriate or maladaptive host responses. Patients infected with filoviruses exhibit generalized fluid distribution problems, hypotension, coagulation disorders, and hemorrhages, finally resulting in a fulminant shock and death.

About GTC

GTC Biotherapeutics is a leader in the development, production, and commercialization of therapeutic proteins through transgenic animal technology. GTC currently has four internal proprietary products in its pipeline and a portfolio of external program production opportunities. In addition to the ATryn(R) program, GTC is developing a recombinant human albumin, a malaria vaccine, and a CD137 antibody to treat solid tumors. In its external programs, GTC's technology is used to develop transgenic production of its partners' proprietary products, including both large-volume protein therapeutics as well as products that are difficult to produce in significant quantities from conventional recombinant production systems. GTC's external program collaborations are developing transgenic versions of products such as monoclonal antibodies and immunoglobulin fusion proteins for conditions such as rheumatoid arthritis, HIV/AIDS and cancer. One of the external programs is in clinical trials with a transgenically produced product. Additional information is available on the GTC web site, http://www.gtc-bio.com.

About USAMRIID

USAMRIID, located at Fort Detrick, Maryland, is the lead medical research laboratory for the U.S. Biological Defense Research Program, and plays a key role in national defense and in infectious disease research. The Institute's mission is to conduct basic and applied research on biological threats resulting in medical solutions to protect military service personnel. USAMRIID is a subordinate laboratory of the U.S. Army Medical Research and Materiel Command.

Forward-Looking Statement for GTC

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 use of ATryn(R) in hemorrhagic diseases and anticipated evaluations of this potential, the EMEA submission for the use of ATryn(R) in HD and the anticipated timing for a European market launch of ATryn(R). 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 as 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 partners and regulatory agencies, and the uncertainty that the Company will be able to obtain additional revenues and financial resources, including through continuing and new external programs and marketing and strategic partners for some of its internal programs. 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.

The information contained in this press release does not necessarily reflect the position or the policy of the Government and no official endorsement should be inferred.