Down on the Pharm
By David Adam
April 30, 2007
A new breed of genetically modified crops could provide cheap drugs and vaccines for the developing world. Only one problem: what if they get into the food chain? Environment correspondent David Adam reports on 'pharming', the new GM front line
In a windowless room on the roof of a hospital in south London, the air is being slowly sucked away. It's not enough to notice, but it keeps the sealed laboratory at a slightly lower pressure than the air outside. It's a security measure. The contents of this laboratory are highly controversial, and if anything escaped it would be a public relations disaster for the scientists who work here. The lab holds some of the most controversial plants in the UK, which nearby residents would be less than happy to find drifting on the breeze through their back gardens. Open the door, and air rushes in, not out. The plants are tobacco, but they are not intended to be smoked. Instead, the scientists who work on them believe they could save lives. Each has been genetically engineered to carry a gene that is usually found in common algae. Inside its cells, the foreign DNA forces the tobacco plant to churn out a protein that is useless to it, but that happens to be a potent drug against HIV. The scientists say the drug, and others like it, could save millions of lives across the developing world. The technique has been dubbed pharmaceutical farming, or pharming, and it is emerging as the latest battleground in the war over genetic modification.
Britain has rejected GM plants once already - a media and consumer backlash persuaded most companies there was little market in the UK for crops that have had their genes tweaked to be resistant to pests or herbicides. But with pharming the battle lines are less clearly defined, as protesters who trashed experimental GM corn plants in France discovered. The crops were making a protein that could be used to treat cystic fibrosis, and when patient groups angrily denounced the action, mainstream green campaigners were forced to deny involvement.
To the scientists developing this new generation of GM plants, the benefits are clear. Conventional ways to make modern medicines are expensive, which means pharmaceutical companies generally target those diseases that affect lots of people who can pay. Plants can be grown, harvested, and the useful medicine purified from them at a fraction of the price, so using them as leafy drug factories saves a fortune, and opens the doors to treating people in poorer countries. Advocates say just 250 acres of GM potato crop could churn out enough hepatitis B vaccine to protect the entire population of south-east Asia from the disease for a year.
But there are concerns too. As with GM food crops, there are fears about whether pharmed plants could breed with wild relatives and disturb the natural gene pool. They could find their way into the food chain - potentially exposing people to uncontrolled doses of potent drugs. And then there is the yuk factor, because the experiments often mingle plant and human genes. The Daily Mail says there are "serious ethical concerns about such a fundamental interference with the building blocks of life".
Professor Julian Ma leads the GM tobacco project at the Centre for Infection at St George's Hospital, in south London, and is responsible for the plants on its roof. He is passionate about the benefits of pharming; he insists they could give hope to millions: "The advantages they offer simply cannot be equalled by any other system. They provide the most promising opportunity open to us to supply low-cost drugs and vaccines to the developing world." Other scientists across the world are growing plants that have been given the genetic instructions to make antibodies, vaccines against disease such as rabies and hepatitis B, and dietary supplements.
The HIV drug produced by the London tobacco plants is called cyanovirin-N, which can help stop the virus entering human cells. Experiments with rhesus macaques, which have a similar reproductive physiology to humans, have suggested that the drug could dramatically cut transmission of the virus during sex, and the St George's team wants to turn it into a cream that could be applied by women in countries where men are resistant to using condoms. "If you're a woman in sub-Saharan Africa, you're not going to pay even a dollar or two a week for this. It has to be pennies, and that means it has to be produced in plants," Ma says. He reckons five tonnes of cyanovirin-N would be needed for 10 million women to have two doses a week - a production scale way beyond the economics and capabilities of conventional drug manufacturing.
He is frustrated by the attitudes to genetic modification in the UK and has little time for the "ethical" arguments against placing human genes into plants because, he says, medicines from GM organisms are nothing new. Growth hormones and insulin, routinely taken by a million diabetes sufferers in Britain, are made by adding the relevant human genes to bacteria and growing the GM bugs in vats to produce the human proteins - a fundamental interference with the building blocks of life that has been widely accepted since the 1980s. (Although a minority of diabetes sufferers do object to GM insulin and request older-style drugs made from animals.)
"From a scientific point of view there really isn't anything special about plants with drugs in them," Ma says. "We can't divorce the science from public attitudes, but life is all about risk assessment and it just isn't feasible to make enough of these medicines in any other way."
Neither is it feasible to make enough from a few plants on a hospital roof, which is why the team is also growing the GM tobacco on a Kent farm, in ultra-secure greenhouses with twin-skin plastic walls strong enough to resist a hurled brick. Ma says these are the botanic equivalent of the containment facilities used by microbiologists to work on biological weapons - a level of security he calls "ridiculous".
Conventional drug manufacturers have shown little interest in pharming technology. With a few exceptions, the big companies do not smell big profits in the vulnerable people or regions of the world that would benefit most. Monsanto, the agrochemical giant behind many GM food crops, closed down its pharming efforts in 2003. The field is now largely the domain of university scientists and small biotechnology companies, several of which have found the financial going too tough and folded. As a result, progress has been slower than expected and no drug produced in a genetically modified plant has yet cleared clinical trials and been given a licence.
When such a medicine comes, it is likely to be in North America, where opposition to GM technology is milder and transgenic crops such as maize and cotton are already grown on a massive scale. The California-based company Ventria Bioscience is developing rice that produces anti-bacterial proteins found in human breast milk and saliva, and recently got permission to grow it across 200 acres of farmland in Kansas. Eventually, the company wants to plant closer to 3,000 acres, which would give it enough drug to conduct the large-scale human trials needed before approval for such a medicine would be granted. It says the proteins in its rice, lactoferrin and lysozyme, could treat children with diarrhoea, a major killer in the developing world.
To some, this rice-growing on open farmland is a step too far. As Helen Wallace of Genewatch, a British campaign group, points out: "If they put these genes into food crops then it is only a matter of time until there is a mix-up and they get into the food chain." And the US agricultural system does have a patchy record on keeping GM and conventional produce separate. Starlink, a variety of GM corn meant only for animal feed, turned up in taco shells sold as snacks across the US in 2000, and Prodigene, a Texas biotech company, was fined $250,000 in 2002 for contaminating a soybean crop with corn engineered to produce an experimental pig vaccine.
In a statement, the USA Rice Federation, an industry body, said: "If Ventria's pharmaceutical rice were to escape into the commercial rice supply, the financial devastation to the US rice industry would likely be absolute. There is no tolerance, either regulatory or in public perception, for a human gene-based pharmaceutical to end up in the world's food supply."
But to the companies developing drugs in plants, food crops such as rice offer a quicker and cheaper route than alternatives such as tobacco. They tend to produce more protein and it stays stable for longer - which means the sensitive medicines do not have to be harvested and processed immediately. Because of this, corn, soybean and wheat have also emerged as popular choices for commercial pharming - to the distress of even previously ardent supporters of GM technology. In an editorial in 2004, Nature Biotechnology, the traditionally pro-industry science journal, said: "It seems an industry in which the PhD is the intellectual norm is either incapable of learning a simple lesson from the past or cannot bring itself to act appropriately, despite what it has learned previously ... This position is not anti GM - we should be concerned about the presence of a potentially toxic substance in food plants. After all, is this really so different from a conventional [drugs] manufacturer packaging its pills in candy wrappers?"
New Scientist magazine has repeatedly pleaded with scientists not to grow drugs in modified food crops, a move it calls "daft". A 2005 editorial said: "Some ideas, no matter how good they look on paper, should never be tried in practice. One of these is producing drugs or vaccines in genetically engineered food crops. The risk of these potent chemicals finding their way into the human food chain is just too high."
To some campaigners, even these statements do not go far enough. They want a ban on any pharmaceutical plant grown outdoors. "It's important not to use food crops and it's important not to grow any GM plant out of containment," Wallace says. "The benefits are still unproven and with any product designed to have an effect on human health, there could also be unforeseen side effects."
Ma argues that such a hardline approach means the main benefit of pharming - scale - will never be fully realised. He says also that different standards are being applied, purely because the technology is labelled as GM. While some farmers in Britain grow rape seed for food, others produce a variety high in a natural chemical called erucic acid, an additive for the plastics industry. "That is much more toxic that anything I grow," he says. Of lysozyme, the saliva protein engineered into Ventria's rice, he says: "If you want to stop that getting into the environment, you need to stop people spitting in the street."
GM scientists now come armed with a battery of new technologies to stop cross-contamination from their plants, he adds. These include growing sterile varieties of the plants, fluorescent markers to identify stray seeds, and genetic tricks to stop the foreign genes appearing in pollen. And, unlike GM food producers, the scientists have a strong interest in keeping their plants isolated. Also, since the aim is to produce medicine, each step of the pharming process is subject to strict regulations. "You have to make sure that people don't walk into your field and have a picnic and mistakenly eat your crop," he says. "But I'm equally concerned that I don't contaminate my plants with food."
Other companies are soon expected to follow Ventria's lead and request permission to plant large amounts of pharmaceutical plants outdoors, and will probably face similar opposition. One enterprising company, Controlled Pharming Ventures, thinks it has a solution: it has converted an old limestone mine in Indiana into an underground drug farm. Experts at nearby Purdue University have already succeeded in producing corn down there, inside a giant illuminated room.
Others think they can find places sufficiently remote to manage the risk of cross-contamination to wild plants - in irrigated plots in arid regions across southern Spain or Africa, for example. The Icelandic company ORF Genetics is producing antibodies and vaccines inside the only barley cultivated anywhere on Iceland (the theory being that whatever it puts in the barley can't jump ship without any other barley to jump to). But to critics of GM technology, even those safeguards are unlikely to be enough, because contamination of food supplies could still occur after the pharma crops have been harvested and processed. (For example, seeds might get mixed up in a factory.)
So Ma and his pharming colleagues around the world are pinning their hopes on an unlikely ally: public opinion. Ma says people opposed to GM crops for food would be much more likely to accept them for medicines because the benefits to society are so much clearer. "The most important thing is to get that first product out there, then people will realise what we can do," he says. Until then, his tobacco plants will remain locked securely away, swaying only in an artificial, heavily filtered breeze.