GTC BIOTHERAPEUTICS TO HOST SECOND QUARTER 2010 EARNINGS CALL AND WEBCAST ON TUESDAY, JULY 27, 2010

FRAMINGHAM, MA –July 20, 2010-- GTC Biotherapeutics, Inc. ("GTC", OTCBB: GTCB.OB) announced today that its financial results for the second quarter 2010 will be released on Tuesday, July 27, 2010 followed by a webcast conference call starting at 10:00 a.m. Eastern Time. You may access the live internet broadcast or the subsequent archived recording, on GTC’s website at http://www.gtc-bio.com or access the conference call as follows:

Live Call – In the United States, dial 1-877-407-0778
Outside the United States, dial 1-201-689-8565

Audio Archive – In the United States, dial 1-877-660-6853
Outside the United States, dial 1-201-612-7415
Reference call ID: when prompted Account #: 286 Conference ID #: 354158

NOTE: a replay of the call will be available one hour following the end of the call and will be accessible until July 26, 2011.

GTC Biotherapeutics’ core technology enables the development and manufacture of 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 therapeutic product produced in transgenic animals to be approved anywhere in the world. In addition to ATryn, GTC is developing a portfolio of recombinant human plasma proteins with known therapeutic benefits. These proteins include a recombinant form of human coagulation factor VIIa, which is being developed with partner LFB for the treatment of patients with hemophilia. GTC has also developed a portfolio of monoclonal antibodies (MABs) targeting HER2, EGFR and TNF, which address markets with total sales in excess of $16 billion, as well as a CD20 antibody with enhanced ADCC (antibody-dependent cell-mediated cytotoxicity).

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 highly flexible and 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.

CONTACT:
GTC Biotherapeutics, Inc.
William K. Heiden
Chairman, CEO and President
(508) 370-5277 or william.heiden@gtc-bio.com