GTC Biotherapeutics Inc announced the initiation of a safety and efficacy study of its recombinant human antithrombin III (rhATIII) for the treatment of patients with a hereditary deficiency (HD) of the antithrombin blood protein. This trial will be conducted in those patients who are in high risk situations for the development of thromboses. The first patient has received treatment in the study. This study is expected to be the final clinical trial before submission for European registration.

"We are pleased with our continuing progress toward the development of rhATIII in Europe for the hereditary deficiency indication," stated Geoffrey F. Cox, GTC's Chairman and CEO. Dr. Cox continued, "We remain on track to complete the safety and efficacy trial in 2003 and make the first filing for approval in Europe of a recombinant antithrombin product in the first half of 2004."

The trial is an open-label, single-arm study including at least twelve patients. This is a multinational study conducted primarily in Europe in hereditary antithrombin deficient individuals that are surgical patients, pregnant patients scheduled for cesarean section or delivery induction, as well as pregnant patients in active labor. Patients are treated with rhATIII during the high risk period. The study is anticipated to take about a year. This clinical trial will assess the incidence of deep vein thrombosis (DVT) following prophylactic intravenous administration of rhATIII to the hereditary deficient patients. A variety of standard safety evaluations will also be performed, including documentation of any adverse events.

A pharmacokinetic study of rhATIII was recently completed in 15 hereditary antithrombin deficient patients in Europe. Infusion of rhATIII was well tolerated and no serious adverse drug reactions were reported.

GTC produces bulk rhATIII from the milk of transgenic goats. Investigational rhATIII is purified from the bulk milk product. The human antithrombin blood protein has anticoagulant and anti-inflammatory properties. Individuals with a deficiency of antithrombin are at risk to develop thromboses, particularly during situations such as surgery, pregnancy and childbirth. About 1 in 2,000 to 1 in 5,000 people have hereditary deficiency of antithrombin.

GTC will host an exhibit booth focused on the antithrombin program at the American Society of Hematology (ASH) Annual Meeting and Exposition in the Philadelphia December 7 through December 10.