For the 800,000 people in the United States who suffer a stroke each year, the window for drug therapy closes in the first few hours after the attack. That leaves some seven million stroke survivors in this country alone with no medical alternative beyond physical therapy. A small pharmaceutical company in New York hopes to change that with a drug that may help patients regain some of their lost mobility six months or more after a stroke.

Strokes happen when blood stops flowing to part of the brain, often due to a blood clot. Without blood to bring new oxygen, cells in the affected region start to die. If the symptoms of stroke are recognized quickly enough and the victim is brought to a hospital within a few hours, doctors can administer a clot-dissolving drug to minimize the damage. But only a small fraction of stroke patients seek medical attention soon enough for this intervention.

"If they miss this therapeutic window, the consequences are heavier, so it's important to be able to do something for those patients who miss that window," says Francesca Bosetti, a stroke expert with the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health.

In the future, stroke patients who miss this window and are affected by reduced mobility long after their stroke may be able to turn to a drug that helps damaged nerves transmit electrical signals in the brain.