FRAMINGHAM, MA, February 15, 2005 - GTC Biotherapeutics, Inc. ("GTC", Nasdaq: GTCB) announced today that Geoffrey Cox, Chairman and CEO of the Company, is scheduled to present an update on GTC's product and corporate development on Wednesday, February 23, 2005 at 11:00 a.m. during the BIO CEO & Investor Conference. The conference is being held at the Waldorf Astoria in New York City from February 23 through February 24, 2005. The presentation will be webcast live and can be accessed by logging onto www.gtc-bio.com. The replay can be accessed from this same website and will be available within 24 hours of the presentation. GTC Biotherapeutics is a leader in the development, production, and commercialization of therapeutic proteins through transgenic animal technology. GTC currently has five products in its internal pipeline and a portfolio of external program production opportunities. GTC's lead program is ATrynŽ, its recombinant form of human antithrombin. A Market Authorization Application is under review by the European Medicines Evaluation Agency for the use of ATrynŽ in patients with a hereditary antithrombin deficiency. In addition to the ATrynŽ program, GTC is developing a recombinant human albumin, a recombinant human alpha 1 antitrypsin, a malaria vaccine, and a CD137 antibody to stimulate the immune system as a potential treatment for 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 transgenically produced 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. CONTACT:
GTC Biotherapeutics
Thomas E. Newberry
Vice President, Corporate Communications
(508) 370-5374 Feinstein Kean Healthcare
Francesca DeVellis (investors)
Barbara Askjaer (media)
(617) 577-8110
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