Doctors would like to quickly dissolve the clots in brain arteries that cause about 80 percent of all strokes, the third leading cause of death behind heart disease and cancer. The only widely available treatment, a bioengineered human protein called TPA, has drawbacks and is given to only about 5 percent of U.S. stroke victims. If used improperly, the drug can trigger disastrous bleeding and another of its limitations is that it must be given within three hours of the start of stroke symptoms. Many victims, hoping their symptoms will go away, do not get to the hospital quickly enough.
So, in search of something better, researchers have been experimenting with another natural anticlotting substance, the saliva of Desmodus rotundus, the vampire bat. The hope is that the active protein, called desmoteplase, will be more precisely targeted at clots and can be used several hours longer after symptoms begin.
In theory, desmoteplase may break up blood clots in the brain without affecting the rest of the body's clotting system and with less risk of hemorrhaging inside the head. It works for the vampire bat, a one-ounce, grayish-brown creature that ranges over Central and South America and preys mostly on livestock. The protein keeps its victims' blood flowing clot-free so it can feed.
Researchers have tested several different doses of desmoteplase and sixty percent of those getting the largest amount had an excellent recovery after three months, compared with 22 percent in the untreated comparison group.
Doctors were especially impressed that only one patient getting the saliva protein suffered brain bleeding. Additional testing will be conducted.
