Bat Saliva Drug and MRI Techniques Offer Hope for Acute Stroke

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(Siemens Medical Solutions)

The use of a synthetic drug derived from the saliva of vampire bats appears to extend the time window for treatment of acute ischemic strokes from three hours to nine hours after symptoms first appear, according to the results of a new international study.

The results of the DIAS trial (Desmoteplase in Acute ischemic Stroke) show that the drug desmoteplase is effective in preventing brain damage from stroke if administered soon after symptoms begin.

The University of Wisconsin (UW) Medical School, Madison, is one of the test sites for the ongoing twin U.S. study, DEDAS (Dose Escalation Study of Desmoteplase in Acute ischemic Stroke), designed to identify the appropriate dosage and effectiveness of the drug.

"This new approach to acute stroke treatment is novel in two ways: It uses an improved clot-dissolving drug and also takes advantage of new MRI techniques to help select the right patients for treatment," says Howard Rowley, MD, associate professor of radiology at the UW Medical School and lead radiologist for the DEDAS study. "The results of the DIAS study are even more exciting as they show specifically how the use of the drug significantly extends the time during which treatment can begin after the onset of stroke symptoms, from three hours to nine hours."

Desmoteplase is a genetically engineered version of a blood clot-dissolving protein from the saliva of the vampire bat, Desmodus rotundus. Desmoteplase is able to dissolve a blood clot without affecting the rest of the body's clotting system and without increasing the risk of intracranial bleeding.

The DIAS study was a multi-center, phase II study. Forty-four hospitals in Europe, Australia and Asia participated and 25 centers recruited a total of 102 patients. Patients eligible for standard treatment received it, but those who met study criteria and were between three to nine hours of initial symptoms were randomly assigned to receive either desmoteplase or a placebo. Neither the researchers nor the patients knew which substance the patient received. The sister study, DEDAS, is ongoing in 17 centers and expects to recruit more than 100 patients in the United States, with the same study design. In both studies, MRI was used to identify patients who have the potential to benefit most from this therapy.

By imaging the brain of stroke victims, the researchers were able to better determine if the patient might be a candidate for desmoteplase. For eligible patients, administering desmoteplase allowed the blood flow in the damaged area of patients' brains to be re-established and the area of damage limited. Ultimately, an effective but safe dosage of desmoteplase was identified, resulting in an extended time window of nine hours vs. three hours.

"The impact of these results cannot be overstated," says Rowley. "Buying more time to treat stroke symptoms – and the ability to safely restore blood flow to the brain – means we can give acute stroke victims hope for a better outcome, even if having a stroke cannot be prevented. It also appears that new MRI techniques are key in helping to select the right patients for therapy."

For more information, call 608-263-2400 or visit www.wisc.edu.

— University of Wisconsin