A new drug appears to protect the brain against damage from stroke, even if administered hours after the stroke occurs, according to a new study in monkeys.
Monkeys given the drug had less dead brain tissue and showed more improvements on tests of brain function after a stroke, compared with monkeys that did not take the drug.
Testing on primates was important because, over the last half-century, there have been more than 1,000 drugs aimed at preventing brain damage that have failed to work in people, even though they worked well in mice or rats, said study researcher Dr. Michael Tymianski, of the Toronto Western Hospital Research Institute in Canada.
The new findings show it is possible to protect a complex brain, similar to that of a human, against damage after stroke, Tymianski said.
In fact, Tymianski and colleagues have already tested the drug, which belongs to a group called PSD-95 inhibitors, in a small number of people. Their early studies suggest the drug is safe and effective in people as well, Tymianski said, and he hopes the drug will be available for people in three to four years.
The researchers induced strokes in cynomolgus macaques. Ten monkeys received the drug, delivered intravenously, while ten received a placebo. To increase their study's validity, the researchers stimulated strokes were likely larger than what would occur in people, Tymianski said.
The monkeys' brains were scanned using magnetic resonance imaging (MRI) one day and 30 days after their strokes, and the animals completed tests over the month to measure their brain function.
The drug reduced the amount of brain tissue at risk for damage by 55 percent after one day, and by 70 percent after one month, the researchers said.
Monkeys given the drug improved on the brain function tests over the study, while monkeys given the placebo did not.
Similar findings were seen even when the drug was administered three hours after stroke, Tymianski said.
"It looks really promising," Dr. S. Thomas Carmichael, a neurologist at the University of California, Los Angeles, said of the findings. "They addressed a lot of past failings that have plagued this area of research," said Carmichael, who was not involved in the study.
PSD-95 inhibitors are thought to work by protecting brain cells from the destructive events that occur when cells are deprived of oxygen, as is the case with stroke. Several other research groups are also investigating their use as stroke treatments.
Some are concerned the drugs may be toxic in people because they inhibit the interactions of a brain protein required for normal brain function, said Dave Schubert, a professor and at the Salk Institute in La Jolla, Calif. And drug toxicity is usually revealed in late-stage clinical trials, because those patients receive the drug for much longer, Schubert said.
The study in monkeys is published today (Feb. 29) in the journal Nature. The researchers presented the findings from their studies in people this year at the International Stroke Conference.
Tymianski is president and CEO of NoNO Inc., a biotechnology company that makes NA-1, the drug used in the study.
Pass it on: Drugs known as PSD-95 inhibitors can protect monkey brains from damage after stroke, and the researchers hope the findings will be true in people too.