San Diego ? Considering the lack of good treatments for strokes, it probably is no surprise that researchers will consider just about anything. But still, vampire bat saliva?

New data released Saturday suggest that idea, farfetched as it sounds, actually may work.

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. But their 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. One of its chief 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.

In the first of two midsize studies on the approach, doctors in Europe, Australia and Asia randomly gave either a genetically engineered version of the saliva protein or dummy injections to 104 stroke victims. All had suffered their strokes within three to nine hours.

Dr. Steven Warach, chief of stroke therapy at the National Institute of Neurological Diseases and Stroke, presented the results at a meeting of the American Stroke Assn. in San Diego.

The researchers tested several different doses. Sixty percent of those getting the largest amount had an excellent recovery after three months, compared with 22 percent in the untreated comparison group.