AR-News: Bat Saliva May Offer Stroke Treatment

[jim robertson]

Bat Saliva May Offer Stroke Treatment
Sat Feb 7, 2:59 PM ET  Add Health - AP to My Yahoo!


By DANIEL Q. HANEY, AP Medical Editor

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.


Certainly, it works for the 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.


In the first of two mid-size 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 the previous 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 Association 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.


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


The study was sponsored by Paion, a German company developing desmoteplase. 
A similar study, still under way, is expected to enroll more than 100 
patients at 17 hospitals in the United States. Already being planned is a 
much larger study intended to prove the drug's safety and effectiveness.


"These are very important results, because they suggest that with a 
different drug we can extend the therapeutic window from three hours, which 
is pretty severe when trying to get patients to treatment," said Dr. Michael 
Moskowitz of Massachusetts General Hospital.


Doctors were especially impressed that only one patient getting the saliva 
protein suffered brain bleeding.


"It's very good that bleeding is not occurring," said Dr. Daniel Hanley of 
Johns Hopkins University. "That, of course, will require further study to be 
sure."


The researchers gave MRI scans and limited treatment to patients who had 
significant amounts of brain tissue that was at risk of dying but still was 
potentially salvageable. Warach said about half of all stroke patients seen 
after three hours fit this criteria.


"There are patients we can help after three hours and maybe even after nine 
hours," Warach said.

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