Pharming is a portmanteau of farming and "pharmaceutical" and refers to the use of genetic engineering to insert genes that code for useful pharmaceuticals into host animals or plants that would otherwise not express those genes. As a consequence, the host animals or plants then make the pharmaceutical product in large quantity, which can then be purified and used as a drug product. Some drug products and nutrients may be able to be delivered directly by eating the plant or drinking the milk. Such technology has the potential to produce large quantities of cheap vaccines, or other important pharmaceutical products such as insulin.
The products of pharming are recombinant proteins or their metabolic products. Drugs made from recombinant proteins potentially have greater efficacy and fewer side effects than small organic molecules (which are often screened as potential drugs) because their action can be more precisely targeted toward the cause of a disease rather than treatment of symptoms. Recombinant proteins are most commonly produced using bacteria or yeast in a bioreactor, but pharming offers the advantage to the producer that it does not require expensive infrastructure, and production capacity can be quickly scaled to meet demand. It is estimated that the expense of producing a recombinant protein drug via pharming will be less than 70% of the current cost.
In the United States, Transgenic plants including but not limited to those that produce pharmaceuticals, are regulated by three government agencies, which comprise the Coordinated Framework for Regulation of Biotechnology established in 1986.
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Expression in the milk of a mammal, such as a cow, sheep, or goat, is a common application, as milk production is plentiful and purification from milk is relatively easy. Hamsters and rabbits have also been used in preliminary studies because of their faster breeding.
One approach to this technology is the creation of a transgenic mammal that can produce the biopharmaceutical in its milk (or blood or urine). Once an animal is produced, typically using the pronuclear microinjection method, it becomes efficacious to use cloning technology to create additional offspring that carry the favorable modified genome.[1] In February 2009 the US FDA granted marketing approval for the first drug to be produced in genetically modified livestock. The drug is called ATryn, which is antithrombin protein purified from the milk of genetically-modified goats. Marketing permission was granted by the European Medicines Agency in August 2006.[2]
Plant-Made Pharmaceuticals (PMPs), also referred to as Biopharming, is a sub-sector of the biotechnology industry that involves the process of genetically engineering plants so that they can produce certain types of therapeutically important proteins and associate molecules such as peptides and secondary metabolites. The proteins and molecules can then be harvested and used to produce pharmaceuticals.
Arabidopsis is often used as a model organism to study gene expression in plants, while actual production may be carried out in maize, rice, potatoes, tobacco, flax or safflower. The advantage of rice and flax is that they are self-pollinating, and thus gene flow issues (see below) are avoided. However, human error could still result in pharm crops entering the food supply. Using a minor crop such as safflower or Tobacco, avoids the greater political pressures and risk to the food supply involved with using staple crops such as beans or rice. Despite these risks, corn and soybeans are currently the most common crops used to produce pharmaceuticals[3].
Recently, several non-crop plants such as the duckweed Lemna minor or the moss Physcomitrella patens have shown to be useful for the production of biopharmaceuticals. These frugal organisms can be cultivated in photobioreactors, secrete the transformed proteins into the growth medium and, thus, substantially reduce the burden of protein purification in preparing recombinant proteins for medical use.[4][5][6]. In addition, both species can be engineered to cause secretion of proteins with human patterns of glycosylation, an improvement over conventional plant gene-expression systems.[7][8].
There is much debate over the practicality of using plants to produce proteins. Some groups fear that contamination of conventional crops might occur; in several instances, companies have been fined for violating protocols, resulting in potential contamination. This leads to the question of "Why would biotechnology companies use plants to produce proteins?"
Conventional production methods for pharmaceutical proteins involve substantial investments of both time and finances. Not only are there manufacturing challenges involved with conventional production methods, but there are also considerable regulatory challenges that must be met. There are currently ~200 protein-based medicines (vaccines, monoclonal antibody drugs, and other therapeutic proteins and peptides) on the market, and ~400 in development. (Statistics are from BIO, the biotechnology trade group) Consequently, companies are motivated to provide a wider range of options for production of proteins used in these treatments.
Biopharm proponents claim that using plants can offer an easily controllable, safe, and cost-effective method for manufacturing proteins, provided that proper regulatory safeguards are put into place to ensure that no outcrossing can occur. It is also important to note, that the global demand for particular pharmaceutical protein can easily be met from just a few acres of pharma-crop, which can be grown under high containment conditions (e.g. in the greenhouse). Some scientists even think that the term "gardening" is more appropriate than farming. Opponents are concerned that there are too many ways in which contamination of the food supply and the environment can occur to make this form of production socially desirable, or even economically feasible.
Compared to conventional production methods, plant-made pharmaceuticals could save substantial time, money, and provide a system for producing proteins that could solve current production challenges.
Although no drugs from pharm crops are currently on the market, open field growing trials of these crops began in the United States in 1992 and have taken place every year since. The United States Department of Agriculture has approved planting of pharma crops in every state, with most testing taking place in Hawaii, Nebraska, Iowa, and Wisconsin[9].
These pharmaceutical crops could become extremely beneficial in developing countries. The World Health Organization estimates that nearly 3 million people die each year from vaccine preventable disease, mostly in Africa. Diseases such as measles and hepatitis lead to deaths in countries where the people cannot afford the high costs of vaccines, but pharm crops could help solve this problem[10].
Companies in this industry hope that proteins made from plants can be used to develop treatments for some of the most serious diseases and conditions such as cancer, diabetes, HIV, heart disease, Alzheimer's disease, cystic fibrosis, multiple sclerosis, Hepatitis C, and arthritis, but no such products have as yet been approved.
Those opposed to pharming fear that through either mishandling or gene flow, potentially dangerous pharmaceuticals may inadvertently enter the food supply. Precedents involving non-pharmaceutical genetically modified crops include the Starlink controversy, and trade war over genetically modified food between the European union and the USA. A similar reaction to pharmed rice is feared from Japan.
In 2002, ProdiGene was fined $250,000 and ordered by the USDA to pay over $3 million in cleanup costs after allowing a fraction of a bushel of volunteer pharm corn to comingle with the soybean crop later planted in that field. Although the chance of gene flow between species is claimed to be low and there was in this case no threat to consumers, the USDA has a zero tolerance policy. ProdiGene has since revised its protocols and resumed operations in Nebraska. In 2005, Anheuser-Busch threatened to boycott rice grown in Missouri because of plans by Ventria Bioscience to grow pharm rice in the state. A compromise was reached, but Ventria has withdrawn its 2006 permit to plant in Missouri due to unrelated circumstances. The company's field trials in North Carolina are expected to continue.
Please note that this list is by no means exhaustive.
Projects known to be abandoned
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