Narcolepsy, a condition that makes people suddenly drop off to sleep, can be the key in finding a new way to ease the life of insomniacs.

Researchers discovered that blocking brain receptors for orexin (hypocretin), a blood peptide important in maintaining wakefulness, induced sleep in rats, dogs and people. Orexin was found absent in the brains of narcolepsy patients.

This chronic condition turn people unable to regulate sleep-wake cycles normally and just in US 135,000 sufferers exist.

The investigation team, led by Francois Jenck of the Swiss drug company Actelion Pharmaceuticals, made a drug able to block the brain receptors to orexin. "The first tests were proof of the concept and the drug is now being evaluated to establish the correct dosage," said Roland Haefeli, an Actelion spokesman.

This year the team should start a phase-three study, which can last several years and would be a detailed check of the drug as a final step before receiving U.S. government approval for its use.

Narcolepsy patients often suffer cataplexy seizures, in which they lose control of muscle tone for a few seconds to minutes.

By now, the drug checks did not reveal any sign of cataplexy.

This research is "promising, with a certain amount of caution", said Dr. Thomas Scammell, an assistant professor of neurology at Harvard University. "I think it may be the beginning of something quite exciting," said Scammell.

The new drug has a different approach than that of the current sleep-inducing pills and the researchers "provide this very broad perspective, all the way from rodents to humans," he said. "The drug may work for people who do not tolerate current sleeping pills well."

"There are concerns that blocking orexin could cause a problem in the brain that is similar to narcolepsy. Subsequent studies will be important to make sure sleep quality is good. Also, cataplexy is difficult to study in the lab because it is often triggered by strong emotions," he said.

"This new compound may give rise to a new family of sleep aids," said Luis de Lecea, an associate professor of psychiatry and behavioral sciences at Stanford University.

"The advantage of targeting orexin is that it involves a relatively small number of neurons. Therefore, it can be much more selective than current sleep aid drugs."

But "Because of the way study was done, it was impossible to determine the sleep quality", warned de Lecea.