Transgenic plants offer a route to making some pharmaceuticals cheaply and effectively, but concerns have been raised that they could pose risks too. Jeff Wolt and his colleagues at Iowa State University argue that the consequences of intended and unintended use both must be considered and managed to understand the risks of such plant-made pharmaceutical proteins (PMPs).
“At this early stage in the development of PMPs case-specific risk assessments are largely lacking in the peer review literature,” say Wolt and co-authors in a paper in CAB Reviews
In terms of the intended drug use, it’s important to know if the PMP will be toxic or allergenic, but also whether the plant itself be toxic or allergenic, on its own or because of the presence of the PMP. Wolt and his colleagues note that also there can be huge variation in the levels of PMPs in plant tissue, so uniformity of dose is a key issue producing medicines this way.
In terms of unintended use, a major concern is that a PMP produced in a food crop could get into the food chain, or that a transgene for producing a PMP could be transferred to other organisms, such as pollinators or soil microorganisms, or wild relatives of the crop.
There are a range of strategies to control the risks of transfer of the genes, such as using male-sterile plants or expression in the chloroplast genome. However, field production of some hazardous PMPs may not be an option.
Wolt and his colleagues say that science-based risk assessment using a case-by-case approach is needed for safe introduction of PMPs. However they conclude “further advancing the application of risk assessment principles for PMPs will require an improved understanding of the human and environmental consequences of occasional low-level environmental occurrences of these highly bioactive substances.”
The paper “Risk Assessment for plant-made pharmaceuticals” by J.D. Wolt, S. Karaman and K. Wang appears in CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2007, 2, No. 012.
Edible vaccines: alternatives to conventional immunization. K. Rowlandson and E Tackaberry. AgBiotechNet 2003, 5, ABN 115, 1-7
The biosafety of molecular farming in plants. U. Commandeur, R.M.Twyman, R.Fischer. AgBiotechNet, 2003, 5, ABN 110, 1-9