Health

Vampire bats, new stroke therapy?

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 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.

Researchers reported Thursday on an experimental device that works like a miniature corkscrew, which can halt strokes by gently pulling blood clots from the brains of victims, but the approach requires much more testing and perhaps refinement. An FDA panel will evaluate the device at the end of the month.

So, in search of something else, researchers have been experimenting with a 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 bat, a 1-ounce, grayish-brown creature that ranges over Central and South America and preys mostly on livestock. The protein keeps its victims' blood flowing so it can feed.

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

Researchers who worked with 104 stroke victims in Europe, Australia and Asia tested several different doses of a genetically engineered version of the saliva protein. Sixty percent of those getting the largest amount had an excellent recovery after three months, compared with 22 percent in the untreated group.

"This is a promising new stroke therapy," Warach said.

- Information from the Washington Post was used in this report.

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