ATryn(R) Receives CHMP Recommendation to Grant Market Authorization; Indicated for Prophylactic Treatment of Hereditary Antithrombin Deficient Patients Undergoing Surgery

GTC Biotherapeutics, Inc. ("GTC", Nasdaq: GTCB)
announced today that the Committee for Medicinal Products for Human
Use (CHMP) of the European Medicines Agency (EMEA) has adopted a
positive opinion on the market authorization application (MAA) for
ATryn(R), GTC's recombinant form of human antithrombin. The CHMP has
recommended that ATryn(R) be granted market authorization for the
prophylaxis of venous thromboembolism in surgery of patients with
congenital antithrombin deficiency. ATryn(R) may be given in
association with heparin or low molecular weight heparin in these
situations. The CHMP opinion recommends granting market authorization
under the EMEA's procedures for exceptional circumstances. Final
market authorization by the European Commission is expected in about
three months. The positive CHMP opinion followed a defined process
this week that included a review of GTC's submission of the grounds
supporting re-examination of the previous opinion as well as a review
of responses to specific questions posed by the CHMP to an independent
expert panel composed of internationally recognized experts in the
fields of hematology and hemostasis. These review activities are an
integral part of the regulatory process for re-examination of a prior
opinion.
Upon approval, ATryn(R) will be the first antithrombin product
approved for use in all 25 countries of the European Union. ATryn(R)
will also be the only available antithrombin product that is produced
by recombinant biotechnology and is not derived from the human blood
supply.
Professor Isobel Walker, Consultant Haematologist, Glasgow Royal
Infirmary, comments that, "It is a good day for European patients with
congenital antithrombin deficiency and for their physicians. ATryn(R)
provides an alternative to treatment with human plasma derived
antithrombin and gives physicians and patients more choice in how they
will be treated."
"Today's announcement marks a very significant achievement for
GTC, being the first company to obtain a positive regulatory opinion
on the commercial use of a therapeutic protein that is produced
transgenically," stated Geoffrey F. Cox, Ph.D., GTC's Chairman of the
Board and Chief Executive Officer. "ATryn(R) presents an opportunity
for hereditary deficiency patients in Europe to choose an antithrombin
product that has met the rigorous examination and review requirements
of the centralized EMEA procedures for recombinant proteins. The
dedication and perseverance of our employees have been instrumental in
GTC reaching this point. We look forward to working with our European
partner, LEO Pharma A/S, to begin the activities required to launch
this product in the marketplace and to support the further development
of ATryn(R) for the treatment of DIC associated with severe sepsis.
The positive opinion is also very supportive of the continuing
development of ATryn(R) in our ongoing study of the hereditary
deficiency indication for a regulatory submission in the United
States. This opinion marks an important step in our strategy to
advance the significant commercial opportunity which we believe
ATryn(R) offers and to unlock the value of our transgenic technology
for the production of therapeutic proteins."
GTC anticipates using the results from both the completed study
reviewed by the CHMP and GTC's ongoing pivotal phase III study to
prepare a Biologics License Application for the United States Food and
Drug Administration. The results of the pivotal phase III study will
also be submitted for consideration by the CHMP for expansion of the
use of ATryn(R) in Europe to prevent deep vein thromboses and
thromboembolisms in women with a hereditary antithrombin deficiency
who are undergoing childbirth.
Antithrombin is a protein in human plasma that has anticoagulant
and anti-inflammatory properties. LEO Pharma has also begun
development of ATryn(R) in Europe as a potential treatment for
disseminated intravascular coagulation, or DIC, associated with severe
sepsis. DIC occurs in an estimated 220,000 severe sepsis cases in the
European Union each year, of which approximately 50% are fatal,
representing a major unmet medical need of significant interest in
critical care.

About GTC Biotherapeutics, Inc.

GTC Biotherapeutics is a leader in the development, production,
and commercialization of therapeutic proteins through transgenic
animal technology. In addition to the ATryn(R) program, GTC has in
development a recombinant human alpha-1 antitrypsin, a recombinant
human albumin, a CD137 antibody to stimulate the immune system as a
potential treatment for solid tumors, and a malaria vaccine. 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. One of GTC's 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.

This press release contains forward-looking statements as defined
in the Private Securities Litigation Reform Act of 1995, including
without limitation statements regarding its expectations for the
European Commission approval of the CHMP opinion, the preparation of a
BLA for filing with the FDA, and potential future consideration of
high-risk childbirth situations. 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
clinical trials and regulatory review of therapeutic products. 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.