Yeast cells offer last line of defense against malaria

Scientists have genetically modified yeast cells to produce an antimalarial drug so powerful that it is regarded as the last line of defense against the disease.

Artemisinin is usually extracted from the delicate sweet wormwood plant, but in recent years, the malaria parasite has developed resistance to almost every other drug on the market, so demand for artemisinin has soared, putting pressure on growers and raising prices.

Large-scale production has been hampered because sweet wormwood takes a year to grow and thrives only in well-controlled climatic conditions.

But according to research published in the journal Nature on Thursday, a chemical cousin of artemisinin can be produced on a mass scale using vats of genetically modified yeast. The chemical can then easily be converted into the drug.

Jay Keasling, who is leading the research at the University of California, Berkeley, said using microbes allows the drug to be manufactured all year round and by scaling up production, a course of treatment would be made at a fraction of the current cost.

"Therapies could be offered significantly below current prices. In addition to cost savings, this bioprocess should not be subject to factors such as weather or political climates that may affect plant cultivation," Keasling said.

The researchers took a type of yeast, Saccharomyces cerevisiae, and modified its cells so they started producing a chemical called artemisininic acid. Because the drug is pushed out of the cells it makes it easy to harvest and purify into a usable drug, Keasling said.

Malaria is one of the world's most devastating diseases, causing illness in an estimated 300 million to 500 million people each year and killing more than a million.

The Bill and Melinda Gates Foundation gave US$43 million to the researchers to develop low-cost drugs to treat malaria using genetically modified microbes.

"It's a big technological advance," said Professor Sanjeev Krishna, a parasitologist at St George's Hospital, London.

"Some of the drugs that are more expensive work some of the time, but we've realized that to really get value for money from them, you have to use them in combination with artemisins, and that increases demand for the drug," he said.