: When vampire bats bite their victims, their saliva releases an enzyme called desmoteplase, or DSPA, into the bloodstream, which causes blood to flow more readily. Several years ago, scientists realized that the same enzyme that gives bats more blood for their bite may also help stroke victims by breaking down blood clots. Dubbed Draculin, this blood-clot-bashing drug has now entered a phase 2 study: In hospitals across the country, scientists are currently comparing Draculin with traditional anticoagulants to see if it increases the three-hour window doctors have to treat post-stroke blood clots. “This is one of the studies that actually extends that window up to 9 hours,” says lead researcher Michel Torbey. “We’re hoping the bat saliva, in itself, dissolves the clot with lower risk of bleeding in the brain afterwards.”What's the Context:
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The most common blood-clot breaker right now is called tissue plasminogen activator, or tPA. The problem is that if it isn't administered to a patient within three hours of a stroke, it does more harm than good. Because a majority of patients don't seek medical help fast enough, "tPA is used in a very small percentage of sufferers."
Researchers discovered Draculin in 1998. A glycoprotein composed of 411 amino acids, Draculin works by inhibiting specific coagulation factors in blood.
In 2003, researchers injected the brains of mice with DSPA and a form of tPA and discovered that DSPA could potentially help more patients than the more common anticoagulant. DSPA attacked fibrin, a fibrous protein that causes blood to clot, without triggering receptors that cause brain damage.
Draculin was first tested on humans in a 2006 study that found that the drug was not only safe, but patients also tolerated it.
If effective, Draculin would help prevent ischemic strokes, a type of stroke caused when blood clots block blood flow to the brain. It accounts for 87% of the 795,000 strokes Americans have each year (the other being hemorrhagic strokes, caused when blood vessels burst).
Not So Fast: Just because Draculin made it past the Phase I tests doesn't mean it's in the clear: Most failed drugs bow out during the Phase II trials, when researchers discover drugs don't work as planned.
Image: Wikimedia Commons / Ltshears