Some researchers are looking to biology to make drugs
Most drug production is based on chemical expertise. But some are produced through biological routes – such as erythropoietin (EPO), which is made by genetically modified mammalian cells grown in culture. Inserting genes in animals or plants to produce drugs has coined the term ‘pharming’.
Proteins are large, chemically complex molecules that would not be easy to make synthetically. But nature has been making them for millions of years, interpreting the information stored in DNA.
It was originally hoped that genetically engineered bacteria might be able to produce therapeutically useful proteins. Unfortunately, it is hard to get mammalian proteins folded properly in bacteria, and they cannot add the multitude of sugars that many proteins have attached to them. Yeast cells and cultured mammalian cells have been used instead.
An ambitious attempt has been made to speed up production of the antimalarial drug artemisinin in yeast. Currently, it has to be extracted from the sweet wormwood plant. Researchers have successfully created yeast that produces artemisinic acid, which is relatively easy to convert into artemisinin. This semi-synthetic antimalarial is now in the process of being produced on a large scale.
A neat solution would be to engineer animals so they produced medicines in their milk. This could be extracted easily, and the animal could go on making the medicine throughout its life.
About the only successful example, however, is Atryn – antithrombin, a protein that inhibits blood clotting – which is produced in genetically modified goats. The FDA approved the product in 2009 to treat patients with antithrombin deficiency. A small number of companies in Europe and the USA are experimenting with a variety of domesticated animals to produce medicinal products.
Companies are also exploring the use of genetically modified plants to produce therapeutic proteins. Of particular interest are plants that can be grown within bioreactors rather than expansive fields. Several vaccines are currently being grown in plants. Products have progressed as far as phase II trials in Europe, and commercial products could be on the market elsewhere within a couple of years.
However, these products will present another regulatory challenge. The use of GM plants also raises the controversies associated with GM food crops, although the scale of pharming would be tiny compared with food production. The main fears are about the contamination of non-engineered crops and their escape into the environment. The question of public acceptability might also be significant.