Scientists have raised hopes of developing a cheap new cure for malaria after successful laboratory tests on monkeys.
Low doses of the treatment are said to have cured animals deliberately infected with the disease. The drug works by preventing malaria parasites from reproducing.
Researchers from France, the Netherlands and Colombia say the results are promising, and they suggest that trials on humans might begin within two years.
But it could be the end of the decade before the treatment is widely used.
One of the hurdles the scientists must overcome is how to turn the drug into an easily swallowed tablet.
The most successful tests on monkeys used injections and the team wants to develop versions that could be easily and cheaply delivered in developing countries. That will probably mean altering the main compound in the treatment, known as G25.
Malaria is estimated to kill more than 1m people a year, mainly children in sub-Saharan Africa, although worldwide there may be anything between 300m and 500m cases of the disease annually.
Malaria parasites have now become resistant to most drugs and with the explosion in cheap international travel, more cases of the disease are being imported into developed countries.
The disease is spread by blood-sucking mosquitoes, whose parasites enter the bloodstream of human victims and burrow into liver cells.
There they multiply by up to 30,000 thousand times in about a week before emerging to infiltrate red blood cells. The new treatment, using G25, targets the parasites' life cycle at this stage - before they produce some 20 offspring. The parasites are vulnerable to the treatment because it stops them packaging their progeny in protective membranes.
Without such treatment, the parasites erupt from the cells, enter the bloodstream and attack more cells. They can colonise and destroy up to 70% of red blood cells, causing anaemia, fever, convulsions, coma and death.
The scientists - led by a biochemist, Henri Vial, from the French national centre of scientific research - report their promising findings in the journal Science.
They used the drug in Colombia on aotus monkeys, the only primate apart from humans to sustain the parasite most associated with malaria in Africa, and on rhesus monkeys, which sustain another common malaria parasite.
Dr Alan Thomas, a Dutch member of the team, said tests suggested the treatment was rapid-acting.
"A short course of treatment might be very effective over a few days," he said.
"There is probably another year or two of pre-clinical development to show it is effective orally. After that you are talking about a relatively long period of human testing that could take three or four years.
"It seems to be targeted against metabolic pathways that have not yet been targeted by other drugs, so there is no pre-existing resistence to this compound."
