Early Promise for a Blood Thinner Without the Bleeding Risk
Animal study suggests an antibody might provide safer protection against clots
So Renne, who is also affiliated with the University Hospital Hamburg-Eppendorf in Germany, and his colleagues studied mice that were engineered to lack factor XII. They found that the animals could not develop blood clots, but -- like their human counterparts -- did not suffer from bleeding. From there, the researchers developed the 3F7 antibody to block factor XII activity.
The antibody effectively blocked clot formation in rabbits that were placed on a simulation of a heart-lung device. It worked about as well as heparin, the researchers found, but without causing bleeding.
Human studies are still needed, but the researchers already know the antibody blocks factor XII in human blood.
"I think that blocking this target (factor XII) is going to prove very useful in procedures where people have to be hooked up to a machine," Schmaier said.
Anti-clotting drugs are commonly used outside of hospitals, too. Many people take oral medications, such as warfarin (Coumadin), to prevent clots that could lead to a heart attack or stroke. Among these are patients with the heart-rhythm disorder atrial fibrillation and those with artificial heart valves.
Since 3F7 is an antibody, it would have to be injected, Renne explained. So, if it pans out, it could be an alternative to the heparin used in hospitals, but it wouldn't replace the oral medications people use long-term.
However, Renne said, drug companies are looking for oral agents that block factor XII. "That is a longer-term goal," he said.
Schmaier said he expects to see a lot more work aimed at factor XII. "I think this report is the tip of the iceberg," he said.
Several of Renne's co-researchers are employees of the pharmaceutical company CSL, which is developing the 3F7 antibody. Renne is named as inventor on a patent application covering the use of factor XII as a target of anti-clotting drugs.