FDA Approves Orphan Drug ATryn to Treat Rare Clotting Disorder

The U.S. Food and Drug Administration today issued its first approval for a biological product produced by genetically engineered (GE) animals.

The approval is for ATryn, an anticoagulant used for the prevention of blood clots in patients with a rare disease known as hereditary antithrombin (AT) deficiency. These patients are at high risk of blood clots during medical interventions, such as surgery, and before, during and after childbirth.

ATryn is a therapeutic protein derived from the milk of goats that have been genetically engineered by introducing a segment of DNA into their genes (called a recombinant DNA or rDNA construct) with instructions for the goat to produce human antithrombin in its milk. Antithrombin is a protein that naturally occurs in healthy individual and helps to keep blood from clotting in the veins and arteries.

GTC Biotherapeutics, Inc., the manufacturer of ATryn, received approvals from two FDA centers. The Center for Biologics Evaluation and Research (CBER) approved the human biologic based on its safety and efficacy, and the Center for Veterinary Medicine (CVM) approved the rDNA construct in the goats that produce ATryn.

"This product offers an important new treatment option for patients with hereditary antithrombin deficiency, preventing life-threatening clots that otherwise frequently occur during high risk situations," said Jesse Goodman, M.D., M.P.H., CBER director.

Because hereditary AT deficiency occurs in a small population (approximately 1 in 5,000 people in the United States), the FDA granted ATryn an orphan drug designation. The orphan drug designation system encourages the development of medications for patients with a rare disease or condition.

The agency held an advisory committee meeting in January to seek the opinion of outside experts, who agreed that ATryn is safe and effective. CVM also briefed the committee about the animal drug components of the application.

Hereditary AT deficiency generally is first recognized and diagnosed in teenagers or young adults when they develop clots in their blood vessels, particularly during pregnancy, surgery, or prolonged bed rest.

CBER evaluated two studies that included 31 patients with hereditary AT deficiency who received ATryn to prevent thromboemboli (TE) before, during or after surgery or childbirth. All but one patient had a prior history of at least one TE, which are likely to recur in high-risk situations if left untreated. Only one of the 31 patients treated with ATryn developed a TE. The most common adverse reactions reported were hemorrhage and reactions at the infusion site. These reactions occurred in approximately five percent of patients.

As part of its review of the GE goat, CVM assessed the safety of the rDNA construct to the animals, including a full review of the construct and its stability in the genome of the goats over seven generations. No adverse outcomes were noted. CVM reviewed and concurred with the sponsor's plan to continue to monitor the construct and its expression for the lifetime of the approved product.

During its review, CVM determined that introduction of the rDNA construct did not cause any adverse outcomes to the health of the goats over seven generations. CVM also determined that the manufacturer, GTC, has adequate procedures in place to ensure that food from these goats does not enter the food supply. As part of the approval, CVM specified that these goats cannot be used for food or feed and validated a method suitable for identifying the rDNA construct in both animals and their products.

As required by the National Environmental Policy Act and its implementing regulations, CVM also determined that the GE goats do not cause any significant impact on the environment.

“We have looked carefully at seven generations of these GE goats; all of them are healthy and we haven't seen any adverse effects from the rDNA construct or its expression. I am pleased that this approval makes possible another source of an important human medication,” said Bernadette Dunham, D.V.M., Ph.D., CVM director.

A summary of the information on which the FDA made its approval decision for the rDNA construct in the goats, and CVM's guidance on the regulation of GE animals containing heritable rDNA constructs are available at http://www.fda.gov/cvm/GEAnimals.htm .

ATryn previously received approval from the European Medicines Agency for use in preventing clotting conditions during surgical procedures in patients with hereditary AT deficiency.

ATryn is manufactured by GTC Biotherapeutics, Inc., Framingham, Mass.

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