GTC Provides Update on TG20 Monoclonal Antibody Targeting CD20

GTC Biotherapeutics, Inc. ("GTC”, NASDAQ: GTCB) announced that it has achieved high-level production of TG20; an anti-CD20 monoclonal antibody (MAb). The TG20 MAb, which is produced in the milk of transgenic goats, is being co-developed by GTC and LFB as part of the LFB-GTC joint venture. TG20 has enhanced antibody-dependent cell-mediated cytotoxicity (ADCC), a key feature useful in the treatment of cancer and auto-immune diseases, and it has been shown to have 10-fold enhanced ADCC when compared side by side with rituximab in assays performed with B-cell chronic lymphocytic leukemia, or B-CLL, patient cancer cell isolates.

"This result is an important demonstration of the ability of GTC’s transgenic technology platform to produce monoclonal antibodies with significantly enhanced ADCC”, said Geoffrey Cox, Ph.D., Chairman, President and CEO of GTC Biotherapeutics. "Furthermore, this is a critical milestone in our development of TG20, an antibody that has the potential of providing more efficacious and cost-effective treatments for cancers such as non-Hodgkin’s lymphoma as well as auto-immune diseases such as rheumatoid arthritis”.

About TG20

Under their joint venture, GTC and LFB are developing TG20, a MAb that targets the CD20 receptor of the immune system with target specificity similar to the rituximab MAb (Rituxan^®, MabThera^®). This antibody has demonstrated a significantly higher ADCC than rituximab. ADCC is one of the mechanisms that the immune system uses to kill cells targeted by a specific antibody. Therapeutic MAbs with increased ADCC are believed to offer more potent treatments for oncology indications. Rituximab is used as a single-agent treatment for relapsed or refractory indolent non-Hodgkin’s lymphoma, or NHL, and also in combination with chemotherapy for the treatment of aggressive NHL. Rituximab has received marketing approval in both the EU and the U.S. for rheumatoid arthritis. Worldwide sales of rituximab were approximately $5.6 billion in 2009.

Follow-on Biologics

In addition to TG20, GTC is also developing a portfolio of monoclonal antibodies for use as follow-on biologics. The portfolio includes antibodies targeting HER2, EGFR and TNF, which, together with TG20, address markets with current aggregate sales in excess of $16 billion. Production animals for these follow-on biologics programs are in development, and are already established for the HER2 monoclonal antibody. In 2010, GTC plans to characterize each of these transgenically-derived antibodies as they become available and to initiate non-clinical studies.

About GTC Biotherapeutics

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 therapeutic product produced in transgenic animals to be approved anywhere in the world. Building upon the 2009 FDA approval of ATryn®, GTC is collaborating with its US commercialization partner, Lundbeck Inc., to develop a protocol for a pivotal study of patients with acquired antithrombin deficiencies in cardiac surgery. GTC aims to initiate a clinical trial in this indication in the second half of 2010.

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 being developed for the treatment of patients with hemophilia, and recombinant alpha-fetoprotein, which is being developed for the treatment of Myasthenia Gravis and Multiple Sclerosis. GTC plans to advance its human recombinant factor VIIa program into a Phase I clinical study in the first half of 2010 and its alpha-fetoprotein program into a Phase II study in Myasthenia Gravis in the second half of 2010 after securing a partner for that program.

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 enable 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.

About LFB

LFB Biotechnologies (a French société par actions simplifiée) is both a strategic shareholder in GTC and the strategic partner of GTC in their joint venture called LFB/GTC LLC. LFB is a biopharmaceutical group that develops, manufactures and markets medicinal products for the treatment of serious and often rare diseases in several major therapeutic fields, namely Hemostasis, Immunology and Intensive Care. The LFB Group is the leading manufacturer of plasma-derived medicinal products in France and 6th worldwide and is also among the leading European companies for the development of monoclonal antibodies and new-generation proteins based on biotechnologies. With its strong focus on research, the LFB Group is pursuing a growth strategy that seeks to extend its activities at the international level and develop innovative therapies. In 2008, the LFB Group reported total turnover of 352,4 million euros, an increase of 9%, and invested 66,6 million euros in product development. The LFB Group markets its products in 20 countries around the world.

This press release contains forward-looking statements, as defined in the Private Securities Litigation Reform Act of 1995, including without limitation statements related to the prospects for TG20, including enhanced ADCC, for treating cancers and autoimmune diseases, as well as GTC’s plans to enter into partnerships and advance its development programs relating to recombinant factor VIIa, alpha-fetoprotein, ATryn and monoclonal antibodies for use as follow-on biologics. 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 securing and depending upon partners, designing and conducting clinical trials and pre-clinical studies, developing new biological products and depending 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.