Bat enzyme holds promise in strokes

An enzyme that lets vampire bats freely slurp blood from their prey may help stroke victims survive, Australian researchers say.

And the treatment may be safer than the present approved treatment.

The compound stops blood from clotting and is similar to a commercial clot-dissolving drug, the researchers say in the latest issue of the journal Stroke.

However, the bat saliva enzyme - called Desmodus rotundus salivary plasminogen activator, or desmoteplase - is hundreds of times more powerful than present drugs.

Desmoteplase destroys fibrin, the structural scaffold of blood clots, said Robert Medcalf of Monash University in Melbourne.

"When the vampire bat bites its victim, it secretes this powerful clot-dissolving substance so that the victim's blood will keep flowing, allowing the bat to feed," Medcalf said.

Many scientists have looked to the saliva of bloodsucking animals such as bats and leeches, as well as insects such as ticks, for drugs that can help stop blood clots, because such animals often produce natural anticoagulants. Heart attacks could be treated as well as stroke.

Dozens of drugs based on such compounds are in development.

Desmoteplase is being developed by PAION, a biopharmaceutical company based in Aachen, Germany. It is nearing final phase II/III trials in stroke victims.

Researchers at the company found that desmoteplase is genetically related to the clotbuster tissue plasminogen activator, known as alteplase or TPA and made by Genentech.

For the stroke study, the Australian team injected either desmoteplase or TPA into the brains of mice, then watched how their brain cells survived. TPA could kill brain cells but desmoteplase did not, they reported.

This could mean desmoteplase had the potential to help many more stroke victims than TPA - because it could be given for many hours after a stroke, Medcalf said.

TPA has to be given during a three-hour window of opportunity - during which many people do not even realise they have had a stroke.

"This report provides data suggesting a potential advantage of a type of plasminogen activator derived from bat saliva over TPA, the only Food and Drug Administration-approved treatment for selected patients with acute ischaemic stroke," said Dr Larry Goldstein, of the American Stroke Association advisory committee.

"It needs to be understood that this study is limited to mice without stroke and focused only on toxicity. Whether it actually helps stroke victims remains to be seen."

- REUTERS

Herald feature: Health