Anti-Clotting Drug Thins Risk to Pregnancy and Surgery Patients With Blood Disorder

Pregnancy and surgery patients with a serious blood disorder that causes excessive clotting have responded well to treatment with a man-made anti-clotting protein. Results from a study by researchers at Yale School of Medicine and other institutions were presented December 6 at the Annual Meeting of the American Society of Hematology (ASH) in San Francisco.

The phase III, multi-center clinical trial focused on patients with the blood disorder known as hereditary antithrombin deficiency. Those who received the protein recombinant human antithrombin reported no excessive clotting during treatment or seven days after treatment.

"This is a remarkable technologic feat," said study investigator Michael Paidas, M.D., associate professor in the Department of Obstetrics, Gynecology & Reproductive Sciences, and director of the Women and Children's Center for Blood Disorders at Yale. "We've shown that this genetically engineered protein can prevent complications linked to antithrombin deficiency. Ours is the first team in the United States to use the protein in a clinical trial with pregnant patients."

Antithrombin occurs naturally in the body and acts as a blood thinner that signals when blood is clotting too much. Patients with antithrombin deficiency do not naturally produce antithrombin. Low antithrombin levels can result in excessive clotting, or venous thromboembolic events (VTEs), which can complicate childbirth and surgery. Those with the condition who undergo childbirth and/or surgical procedures are at high risk for pulmonary embolism-a major cause of maternal death.

The genetic deficiency affects approximately one in 2,000 to one in 5,000 people, and half of all people diagnosed suffer a thrombosis before age 25. The deficiency can also be acquired through ailments such as liver disease, malnutrition or severe burns, which can lead to impaired production of antithrombin.

Yale was one of only two U.S. sites to participate in the study, which included 18 patients-12 pregnant and six surgical. Participants with a history or risk of VTE were given an initial dose of recombinant human antithrombin, followed by maintenance doses based on antithrombin levels. The study also showed that new dosing methods could be tailored to individual patients, which helped pregnant patients to achieve and maintain ideal antithrombin levels.

If approved by the FDA, recombinant human antithrombin will be marketed under the brand name ATryn®; the compound was developed by GTC Biotherapeutics and licensed to Ovation Pharmaceuticals, Inc. in the U.S.