FRAMINGHAM, MA, May 16, 2007-GTC Biotherapeutics, Inc. (“GTC”) (Nasdaq: GTCB) will webcast its 2007 Annual Meeting of Stockholders on May 23, 2007 starting at approximately 1:00 p.m. Eastern Time. The annual meeting is to be held at the Forefront Center for Meetings & Conferences in Waltham, Massachusetts. GTC expects to conduct the formal business portion of the meeting followed by a presentation to its stockholders.

To access the 2007 Annual Meeting live via the Internet, please log onto www.gtc-bio.com approximately 15 minutes before the start of the meeting to allow for any software downloads that may be necessary. Following the webcast of the meeting, an archive will be available at the same address.

The webcast is also being distributed through the Thomson StreetEvents Network. Individual investors can listen to the meeting at www.earnings.com, Thomson’s individual investor portal, powered by StreetEvents. Institutional investors can access the call via Thomson StreetEvents (www.streetevents.com), a password-protected event management site.

GTC Biotherapeutics develops, produces, and commercializes therapeutic proteins through transgenic animal technology. In August 2006, ATryn®, GTC’s recombinant form of human antithrombin, was approved by the European Commission for use in patients with hereditary antithrombin deficiency undergoing surgical procedures. This was the first approval anywhere in the world of a therapeutic protein produced from a transgenic animal. Antithrombin is a protein with anticoagulant and anti-inflammatory properties. We have developed goats that have the human antithrombin gene linked to a milk-protein promoting gene so that they express this protein in their milk. This transgenic approach provides the opportunity to produce recombinant forms of proteins, such as antithrombin, that are difficult to express in economically viable quantities in conventional production systems. In addition, GTC has established a strategic collaboration with LFB Biotechnologies of France to jointly develop recombinant forms of human plasma proteins and monoclonal antibodies. The first program of the collaboration will be to develop recombinant human factor VIIa as a potential treatment for hemophilia in patients with antibodies to other coagulation factors.

In 2006, GTC was granted 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 enabling cost effective development of proteins that are difficult to express in traditional recombinant production systems as well as those that are required in large volumes. Additional information is available on the GTC web site, http://www.gtc-bio.com.

CONTACT:
GTC Biotherapeutics, Inc.
Thomas E. Newberry
Vice President, Corporate Communications
(508) 370-5374