GTC Biotherapeutics's ATryn Meets Primary Endpoint

GTC Biotherapeutics's ATryn Meets Primary Endpoint

FRAMINGHAM, Mass. -- GTC Biotherapeutics, Inc. announced today that ATryn® has met the statistical requirements for the primary endpoint in the pivotal study for the treatment of patients with hereditary antithrombin deficiency, or HD, undergoing high-risk surgical or childbirth procedures. The primary endpoint was demonstration of non-inferiority to plasma-derived antithrombin in preventing clinically relevant deep vein thromboses, or DVTs, or other thromboembolisms.

GTC also announced that it has initiated the filing of the associated Biologics License Application, or BLA, by submitting the preclinical and manufacturing sections. The last section to be filed is expected to be the full clinical study results around mid-year, once all reviews of the data have been completed. GTC is seeking priority review in conjunction with the BLA submission, and on that basis anticipates approval of the BLA approximately 6 months after submission of the last section. GTC previously received approval to commence the BLA filing on a rolling basis when ATryn® was granted fast track status by the Food and Drug Administration, or FDA. Separately, ATryn® has also been designated an orphan drug for the HD indication.

The completed comparator arm of the study is based on historical data gathered under a prospective clinical protocol from patients who had been previously treated with plasma-derived antithrombin products while undergoing similar high-risk procedures to those performed in the active arm. There were no clinically relevant DVTs or other thromboembolisms in these patients.

A minimum of 31 evaluable HD patients are required for the ATryn® treatment trial. Results for 14 of these patients were already obtained from the previous study that supported ATryn®’s approval in the European Union for HD patients undergoing surgical procedures. Seventeen additional patients have been treated, of which 16 are considered evaluable. One patient is considered unevaluable due to the course of treatment deviating from the clinical protocol. None of the additional patients had clinically relevant DVTs or other thromboembolisms during the evaluation period. On this basis, the study has already met the statistical requirements for non-inferiority. Although the primary endpoint has already been met, enrollment is being extended through February to include an additional patient to ensure that the minimum number of evaluable patient procedures agreed upon with the FDA is satisfied.

“We look forward to moving into the regulatory review process with the FDA on the basis of having met the primary endpoint for ATryn®’s clinical studies,” stated Geoffrey F. Cox, PhD, GTC’s Chairman and CEO. “We are grateful to the many physicians and clinical sites that supported the most robust clinical study in hereditary deficient patients ever attempted for any antithrombin product. ATryn® is also unique in being the only recombinant form of human antithrombin to be developed for therapeutic use.”

Complete safety and efficacy data will be available for the BLA submission after the last patient is enrolled. The completed clinical data package will include 90-day follow-up tests for antibody generation to ATryn® after the last patient is treated, which is a typical regulatory requirement and was also part of the approval process successfully completed for the European Union.

About GTC Biotherapeutics

GTC Biotherapeutics develops, supplies, and commercializes therapeutic proteins produced through transgenic animal technology. 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, VIII, and IX, and alpha-1 antitrypsin. GTC also has a monoclonal antibody portfolio that includes a CD20 monoclonal antibody and a monoclonal antibody to CD137. 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 enabling 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,

This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, including without limitation statements regarding the timing of completion of enrollment in the comparative study and availability of antibody generation results, and filing and approval of the associated BLA. 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 uncertainties associated with conducting clinical studies, and the risks and uncertainties associated with dependence 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.

Contact: GTC Biotherapeutics, Inc. Thomas E. Newberry