An experimental drug could protect stroke victims from brain damage. The treatment has shown very promising results in animal tests, and early results with humans are also encouraging.

There is currently only one effective treatment for stroke. Tissue plasminogen activator (tPA) can dissolve the blood clots that cause a stroke.

But it has to be given very soon after symptoms appear, and doctors first have to make sure that the stroke was not caused by a ruptured blood vessel, in which case tPA can make the situation a lot worse.

Michael Tymianski and his team, at the Toronto Western Hospital Research Institute in Canada, devised a different kind of stroke treatment, a drug known as a PSD-95 inhibitor. It works by blocking a key protein in the chain reaction of events that leads to brain-cell death.

"So by inhibiting this protein, by having a drug that binds to it so the protein can't do what it usually does, we prevent the formation of a toxic free radical called nitric oxide. And as a result of that, brain cells that are treated with this drug become more resilient to a stroke," he said.

In a new scientific paper published online in Nature, Tymianski has published the results of research on macaques - primates with complex brains much like ours.

"Animals that were treated with the placebo drug got very large strokes and were very disabled from their strokes. But animals that received the drug had much smaller strokes on their MRI scans and they were neurologically much better off."

Those encouraging results have already led to human trials, and Tymianski says "the top-line results of that particular trial have already been announced at the International Stroke Conference in New Orleans in February. So we already know that when this drug is given to humans the same way that it's given to the primates and at the same doses, it reduces stroke damage in the human brain."

Tymianski says that, unlike current treatment with tPA, the PSD-95 inhibitor can help patients with hemorrhagic strokes, which are caused by a ruptured blood vessel, and it may even be useful in treating other brain injuries as well.