科学家尝试开发治疗嗜睡病新药

Researchers say they've developed a safer way to treat sleeping sickness, a parasitic disease that is fatal if not treated.

Sleeping sickness, or trypanosomiasis, is a chronic medical problem in 36 countries of sub-Saharan Africa and treatment for one variety is highly toxic.

Sleeping sickness is caused by two related parasites, producing two varieties of the disease. The form prevalent in West Africa is more common, but the East African variety is more aggressive, and the patient can die within weeks or months of infection.

The parasite first invades the blood and lymph systems, but then crosses into the nervous system, causing symptoms like confusion, behavior change, and daytime sleepiness. Brain infection leads to inflammation and death.

For patients with the East African form of the disease, researcher Peter Kennedy says the only available treatment is itself a serious health risk.

"The problem is, the drugs for the brain disease are very, very toxic," he says. "So, untreated, everyone dies. But treated with this drug, five percent of patients die. This is an appalling figure, which just has to be improved."

Kennedy, an immunologist at the University of Glasgow in Scotland, is a leading expert on sleeping sickness. He explains that the drug, called melarsoprol, has to be injected intravenously, repeatedly, and at increasing concentrations.

So Kennedy and his colleagues combined melarsoprol with another chemical, cyclodextrin. The resulting formula doesn't have to be injected.

"What we find is that it can be given orally. And because of this, it can be absorbed from the gut more slowly. And we believe - although we don't know for sure - that one of the main reasons why it's less toxic is that there isn't this sudden rush of drug into the body, and thereby producing less toxic effects."

In testing on laboratory mice, Kennedy says the combination retained the effectiveness of melarsoprol, without the frequently fatal side effects.

But will it work the same way in humans? Sometimes, new drugs work fine in animal tests, but not with people. Kennedy says, "this is different. This is already a drug that is given to humans. What we've done is we've used the mouse model to change the molecular configuration of the drug so the drug becomes less toxic and effective orally."

Plans are already underway to take this new combination medicine to human trials, starting as soon as the beginning of 2013. If it all works out, he says the melarsoprol-cyclodextrin combination could lower the cost of treatment by reducing hospital stays.