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Larger tests are needed but the test of heavy smokers suggested that 40 percent were able to quit smoking for nearly six months after receiving the vaccine, the researchers said.
Zurich-based Cytos Biotechnology AG plans phase III trials aimed at showing the vaccine is not only safe but works, and is aiming to get it on the market by 2010, Cytos Chief Executive Dr. Wolfgang Renner said.
Speaking to a meeting of the American Society of Clinical Oncology, Dr. Jacques Cornuz of University Hospital Lausanne said the vaccine was based on a bacteriophage, a type of virus that attacks bacteria.
Cytos designed a vaccine that uses part of a protein from the virus, genetically engineered to attract an immune system response to nicotine. Patients who get the vaccine generate antibodies that neutralize nicotine.
"They don't feel that they have to take a cigarette to feel better," Cornuz said in an interview.
For the Phase II study designed to show whether the vaccine is safe and can be tolerated, Cornuz's team tested 341 smokers, of whom 239 also avoided using nicotine replacement therapy such as gum or patches.
Two-thirds of them got five doses of the vaccine, at varying doses, over four months. One-third got a placebo. Everyone was counseled about quitting smoking.
"The whole thing is totally exploratory," Renner said in an interview.
Cornuz's team tested the volunteers for antibody response, and found some produced more than others. Those who produced the most antibody after receiving the vaccine were also the most likely to be able to stop smoking -- 57 percent of them did.
All the smokers who got the vaccine had some sort of anti-nicotine antibody response.
None of the smokers given a placebo produced any anti-nicotine antibodies, although 31 percent of them were able to stop smoking for 24 weeks.
Renner said his company also wanted to make vaccines to treat high blood pressure and Alzheimer's disease. The high blood pressure vaccine would target angiotensin 2, a protein that regulates the blood vessels, which is currently affected by drugs on the market called angiotensin 2 inhibitors.
Renner said high blood pressure patients did not always take their drugs consistently and he believed a vaccine might be a more reliable way to control blood pressure.
Smoking is extremely addictive and on average, it takes 11 tries to quit. Tobacco use is the single largest cause of cancer and heart disease and kills 5 million people a year, according to the World Health Organization