The European Union decided against allowing a protein drug derived from the milk of genetically-engineered goats. In a press release, the European Medicines Agency (EMEA) in London said it had rejected the application to license a natural human protein extracted from the milk of goats. EMEA recommended against approval of ATryn (recombinant antithrombin alpha), which was set to become the world’s first medicine to be produced from a genetically modified animal. The 57 unique goats that produced the drug-laden milk live on a farm belonging to GTC Biotherapeutics.
The Committee for Medicinal Products for Human Use (CHMP) adopted a negative opinion, refusing to allow the marketing authorization for ATryn 1750 IU powder for solution for infusion, to be used in surgical patients with congenital antithrombin deficiency for the prophylaxis of deep vein thrombosis and thromboembolism in clinical risk situations, i.e., during the peri-surgical period. Genzyme Europe B.V. may request a re-examination of the opinion.
ATryn was to be used in patients who have an inherited reduction of the protein antithrombin, to prevent problems due to the formation of clots in the vessels of the legs (deep vein thrombosis, DVT) or in other vessels of the body (thromboembolism) during high risk situations (for example major surgery). ATryn is an anti-clotting agent. The active substance in ATryn, antithrombin alpha, is a copy of the natural blood protein that is produced by recombinant DNA technology. It is extracted from the milk of goats who have a gene (DNA) inserted, which make them able to produce the human protein in their milk.
In the body, antithrombin blocks thrombin, one of the substances involved in blood coagulation (clotting). Thrombin plays a central role in the process of blood clotting. Patients who have a congenital antithrombin deficiency have blood levels of antithrombin that are lower than normal, which may result in a reduced anti-clotting capacity of the blood. This increases the risk of the formation of clots during high-risk situations. ATryn would be expected to correct the antithrombin deficiency and to give temporary control of the clotting disorder.
The disease is rare (it is estimated that about one person in 3, 000 to 5,000 have a congenital antithrombin deficiency), and this explains why few patients have been treated during the studies. However, for the proposed indication, only 5 surgical cases were considered. The CHMP considered this number to be too small, and not in line with the EMEA’s recommendation of 12 patients.
The results in patients treated in the compassionate use program and at childbirth could not be used to support the proposed use in patients undergoing surgery. Also, the process for the production of the medicine used in the studies is not exactly the same as that which would have been marketed (addition of a filtration step). ATryn is a protein-based medicine, and, like all protein-based medicines, it is possible that patients develop antibodies (proteins produced in response to ATryn). The CHMP considered that they did not carry out enough studies looking for the development of antibodies.
At this point in time, the CHMP was of the opinion that it was not yet demonstrated that ATryn’s benefits are greater than its risks. Hence, the CHMP recommended that ATryn be refused authorization in the EU. Progress has been slow in bringing products to market that are derived from animals. It has been nearly 14 years since the birth of GTC’s first ATryn goat, and not a single product has made it to market yet.
