Rather than dissolving clots like t-PA, the experimental drug -- known for now as NXY-059 -- helps brain cells survive the stroke.

For many years, doctors could do little to intervene while an ischemic stroke (a stroke resulting from the blockage of an artery supplying blood to the brain) was in progress. But that changed about a decade ago with the approval of the emergency stroke drug tissue-type plasminogen activator (t-PA), also known as alteplase (Activase). This thrombolytic drug can break up a blood clot that is blocking blood flow to the brain. Once the clot is dissolved, blood starts flowing again and brain injury is minimized.

Now a new drug could allow more stroke victims to get the emergency treatment that aids in long-term recovery, a study reported in the New England Journal of Medicine (Volume 354, page 588) suggests.

Today, someone having an ischemic stroke can receive a "clotbusting” drug called t-PA. The problem is treatment has to be started within three hours of stroke onset. But by the time most people get to the hospital and have the necessary tests, too much time has elapsed and they are no longer eligible for t-PA.

The experimental drug, known for now as NXY-059, doubles that window of opportunity to six hours. Rather than dissolving clots like t-PA, it helps brain cells survive the stroke. In the study, 1,700 patients were randomly assigned to receive infusions of NXY-059 or an inactive solution within six hours of stroke onset. Three months after treatment, those who received the drug had somewhat less disability -- for example, they were more likely to be able to walk without assistance. In addition, 4% more of those treated with the drug had fully recovered. The benefits of NXY-059 in this study were modest. But considering the lasting damage strokes can cause, even modest therapy advances are important. NXY-059 is now being tested in a larger study group.