Scientists have developed a new drug which they say could transform the fight against malaria.
Malaria is spread by mosquitoes
The drug is a synthetic version of Artemisinin, a herb extract that has been used for centuries in China.
Artemisinin-based drugs are already available but the manufacturing process makes them expensive.
Writing in Nature, scientists said they had succeeded in developing a drug in the laboratory that can mimic its effects at a fraction of the cost.
Malaria kills about one million people around the world each year, most of them children. The disease - a parasitic infection - is spread by mosquitoes.
The World Health Organization has set a target to reduce malaria deaths by half by 2010.
However, increasing resistance to the cheap drugs used to treat the disease is threatening that plan.
Artemisinin-based drugs are regarded as the most effective weapon against malaria. However, their high cost puts them out of reach of millions of people in the developing world who need them most.
"Making it is difficult and expensive," said Brian Greenwood, professor of tropical medicine at the London School of Hygiene and Tropical Medicine.
"This is because it takes 18 months to grow and then the drug needs to be extracted."
A factory-made version of the drug that can treat the disease at a fraction of the price could transform the fight against malaria.
Scientists have recently finished animal and laboratory tests on their drug, which they have called OZ. They are now planning clinical trials on humans to see how effective it is.
But the Medicines for Malaria Venture, which has helped to develop the drug, is already hailing it.
"The drug could be the biggest breakthrough in malarial treatment of our generation and could become the most potent weapon against drug-resistant malaria," it said.
However, other scientists have expressed caution. Malaria has shown a remarkable ability to develop and become resistant to drugs that used to beat it. The same could happen with OZ.
"There is always great optimism when a new 'wonder drug' comes along, yet malaria parasites are extremely adept at evolving drug resistance," said Andrew Read, professor of biology at Edinburgh University.
"Let's hope the optimism is well placed this time, though history is not on our side."
That view was echoed by Robert Sinden, professor of parasite cell biology at Imperial College London.
"The fight is not over. Resistance to these drugs will evolve and the search for new drugs, vaccines and other measures to halt transmission of this expanding disease must be pursued with vigour."