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The Globe and Mail

Experimental drug could mitigate brain damage caused by strokes

New Canadian research suggests an experimental drug can help protect the brain during the initial stages of a stroke, providing doctors with extra time to restore normal blood flow and thereby reducing the risks of permanent disability.

Although the study was conducted on macaque monkeys, the researchers think the findings should also apply to people and are eager to move forward with clinical trials.

"We believe this may have great promise for humanity," said lead researcher Michael Tymianski of the Krembil Neuroscience Centre at Toronto Western Hospital.

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There is currently only one treatment for stroke – a clot-busting drug known as tPA (tissue plasminogen activator). But it must be given within 4.5 hours of the onset of symptoms to be beneficial. As well, therapy can't commence until after certain medical tests, including a brain scan, confirm the patient is suffering from an ischemic stroke caused by a clot that blocks blood flow to part of the brain. There is good reason to do these time-consuming precautionary tests; if tPA is given to patients with hemorrhagic strokes – or brain bleeds – it will kill them.

Less than 10 per cent of patients get tPA within 4.5 hours, at which point the brain can suffer permanent damage. As time passes, the loss of oxygen-rich blood sets in motion a chain of chemical reactions that produce toxic free radicals, which kill nerve cells.

The experimental drug – called Tat-NR2B9c – puts a halt to this destructive process.

"We're blocking these reactions, and when you don't get an accumulation of free radicals, the cells don't die," said Dr. Tymianski, who has been developing the drug for more than a decade.

His team's study, published this week in the journal Nature, showed that the drug prevents brain cell death and preserves brain function in non-human primates.

He envisions a day when ambulance paramedics and emergency-room attendants routinely give the drug to anyone showing symptoms of a stroke. Then, with the patient's condition stabilized, doctors could perform tests to determine whether tPA is warranted.

"If you could buy the brain a few more hours, it would lead to an exponential increase in the number of patients who would benefit from reperfusion [clot-busting therapy]" said Dr. Tymianski.

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Of course, lengthy clinical trials will have to demonstrate that the drug works on people. Over the past 50 years, more than 1,000 promising stroke treatments have met with failure, and pharmaceutical companies have grown increasingly reluctant to invest in this area of research.

Due to the lack of industry involvement, Dr. Tymianski and colleagues created their own company, called NoNO Inc., to raise private capital for the drug's initial phases of development. Dr. Tymianski, who is both president and CEO, believes the new stroke treatment could on the market in five years. "I have a huge conflict of interest," he said half-jokingly about his role as researcher and drug company executive. "Nonetheless, if we don't do it, who will?"

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