Scientists have genetically modified yeast cells to make them churn out painkillers that are normally harvested from opium poppies.



The procedure raises hopes for a biological manufacturing route that slashes the time it takes to make the valuable drugs from a year to several days.



Researchers at Stanford University in California believe that with further development, batches of genetically modified (GM) yeast could produce the drugs at one tenth of the cost of conventional poppy routes.



Christina Smolke, a bioengineer at Stanford, reprogrammed the genetic machinery of baker’s yeast to make the cells convert sugar into a close relative of morphine called hydrocodone.



Writing in the journal Science, her team describes how they took 23 genes from plants, bacteria and rats, to equip the yeast with the enzymes they needed to convert sugar into the drug which blocks pain receptors in the brain.



“You can think of it as an assembly line process,” Smolke said. “It starts with sugar which gets broken down, then begins to get built up into more complex molecules.”



The pain-relieving drugs are normally made through a lengthy route that involves licensed farmers growing the poppies and then shipping the plants to pharmaceutical companies to extract the opioid drug molecules. To make a batch of the drugs can take a year.



The traditional method is unreliable as well as time-consuming, as the plants can be damaged by bad weather, pests and disease.



Smolke’s study demonstrates that it is possible to replace the farm-to-factory route with engineered yeast. But the new procedure faces its own hurdles: to make one dose of painkiller would take 20,000 litres of genetically modified yeast cells.



The new technique could be used to make other drugs that fight cancer, infectious diseases, and long term conditions, such as high blood pressure and arthritis, Smolke added.

“With further development it can certainly have a significant difference,” she said. “By our estimates it will reduce the cost by about ten-fold for making these chemicals. That is an important thing because there’s a large percentage of the global population that doesn’t have access to these medicines.”



According to the World Health Organisation, more than five billion people have little or no access to pain medications. Smolke hopes that the new procedure could reduce the price of medicines enough to make them more accessible across the globe.



Tom Ellis, who works on synthetic biology at Imperial College in London, said it is much more challenging to create illegal drugs, such as heroin, from the chemicals produced by GM yeast than those found naturally in poppies.



“We can take the production of these medicines away from reliance on opium poppies and so free it from being related to the illegal drug market, and the farming of poppies in Afghanistan,” he said.



The new route should also give manufacturers more flexibility to make different drug compounds. “In an engineered yeast cell you can change the structure and have more control over what you want to make. There is the potential to make a certain medicinal compound over something you don’t want,” Ellis added.

The next step for the researchers is to boost the efficiency of the GM yeast. The yields of yeast-based painkillers need to rise 100,000 times to challenge traditional opium poppy farming.

Researchers could increase the amount of drug each cell makes by improving the efficiency of the enzymes used, and optimising the growth of the yeast.

“A well-funded company would be able to crack this in five or six years,” said Ellis.



In a separate study, Smolke looked at concerns that the new GM yeast cells could be used by illegal drug manufacturers and dealers to make homebrew opioids. But under homebrew conditions, she failed to get the modified strain to churn out the drugs.

