Plant-Made Pharmaceuticals

Using plants, it is technically possible to grow, harvest, and process pharmaceutical proteins on a large scale. The genetically modified crop containing edible vaccine, for instance, can be consumed raw or partially processed. By targeting protein expression into specific organs of the plant such as grains, one creates a stable storage system. By targeting the recombinant protein to subcellular regions of the cells, such as the endoplasmic reticulum, a favorable environment is created for its appropriate folding and assembly, thus increasing the amount of recombinant proteins produced. Additionally, targeting the recombinant protein to the membrane concentrates the product. As a consequence, the cost of downstream purification is minimized. Finally, using plants for the production of drugs reduces the risk of contamination with human or animal pathogens, unlike production via animal or human sources.

So far, pharmaceutical proteins produced in plants can be classified into three groups: human biopharmaceutical proteins, including growth hormone, human serum albumin, β-interferon, and erythropoietin; recombinant antibodies such as IgG1 and IgM; and recombinant subunit vaccines, from the hepatitis B envelope proteins and the rabies virus glycoproteins to the cholera toxin B subunit.


High-expression levels of recombinant proteins determine the commercial viability of molecular farming. Yields are therefore crucial, as witnessed by the collapse of the US company CropTech in 2003, due to its inability to achieve the expression levels required for commercial feasibility. "Yield is a critical point," says Hilary Koprowski, MD, Thomas Jefferson University, Philadelphia, who pioneered the expression of animal proteins in plants. "You can overcome it by using larger amounts of plants, which are much easier to use than mammalian cells, but we still would like to increase the yields."

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