WIESBADEN – Tobacco has a bright future – not in cigarettes, but as a pharmaceutical production factory for anti-cavities medicine. The US company Planet Biotechnology is using transgenic tobacco plants to cultivate the human protein CaroRx, which could prevent tooth decay in the future.

Tobacco plants are the basis for new medicines. The cultivation of active and additional substances in plants – the so called “molecular farming” – was the topic of discussion among medical practitioners at this year’s Intern Congress in Wiesbaden. For the first time in this country, attention was not focused on the risks of green biotechnology, but rather on its medicinal possibilities.

“CaroRx was the first active substance clinically tested on patients with promising success and no side effects so far,” said Eva Stoeger of the University of Aachen.

Scientists at St. George Hospital London were in charge of the development of the anti-cavity agent, but both Stoeger’s group and the Fraunhofer Institue for molecular biology and applied ecology in Aachen contributed to the project decisively.

Cavities, or tooth decay, is caused by a bacterium, called Streptococcus mutans. It adheres to enamel proteins by means of small protein antennas and processes food sugars into milk acid, which in turn attacks the enamel. CaroRx recognizes these antennas and blocks them “making it impossible for bacteria to dock onto the tooth,” said Eva Stoeger.

Safe and Cheap Bio-Factories

Fighting diseases with biologically active proteins is a well-known strategy. Market leaders such as Genentech or Chiron produce so-called biologicals for the treatment of rheumatism or multiple sclerosis, but their production makes use of transgenic microorganisms, or mammalian cells, rather than tobacco plants.

The problem with using microorganisms is that bacteria deliver the proteins in the form of useless clumps and mammalian cells need to be tested for pathogens that could possibly infect humans. Plants, acting as pharmaceutical factories, are much more economical and flexible, according to the opinion of experts such as Val Glidinger, American Biotechnology Association’s vice president for nutrition and agriculture.

“It’s important to optimize the technical filtering of the proteins from the plants,” said Eva Stoeger. “Guidelines for production will have to be developed, that would have to be valid for traditional pharmaceutical companies, as well. If these obstacles are overcome, plants will turn out to be promising, safe and economical bio-factories,” said Stoeger.

This attitude is greeted with doubt by biotechnology experts in Germany. “The most important thing with therapeutically used proteins is that they have to be constructed and folded precisely,” said Ludger Wess from the information service Biocentury.

“This process is not carried out in identical ways in plants and humans. It is not clear if plants always produce the active substances in the same way and in the same amounts. The vaccine-banana, or the cloned sheep Tracy, that produces an active substance against pulmonary congestion in its milk failed on exactly these accounts,” said Wess.

Promising cavity-prohibiting tobacco tincture

The study results for the anti-cavity tobacco plant agent are nevertheless promising. Dentistry students who applied it at the beginning of the study were cavity-free for one year. For it to be allowed on the market, it will need to prove effective in a phase 3 study with a larger number of patients.

The suspicion toward genetically modified plants is widespread in Europe. It was only a short while ago that the German government passed a law regarding genetic engineering. Many biotechnologists think this law is an effort to stifle their research, as it allows institutes and farmers who sow genetically manipulated seeds to be sued if a neighboring field is contaminated by windborne transgenic pollen by more than 0,9 percent—for most, an incalculable risk. At the same time, the European Union is supporting a new project to develop vaccines against rabies, tuberculosis, diabetes and HIV from plants. The first tests with these medications are expected in 2009.