Scientists have devised a vaccine for smokers which prevents them from gaining pleasure from nicotine.
A single dose of the vaccine allowed the liver to produce antibodies that stopped most of the nicotine from getting to the brain, according to a study published yesterday in the US journal 'Science Translational Medicine'.
The researchers carried out their experiments on mice, and it showed that levels of nicotine in the brain were reduced by 85pc after vaccination.
Years of research are still needed before it can be tested on people.
However, Prof Ronald Crystal, who led the research team, is convinced there will be benefits.
Of the more than 4,000 chemicals in cigarette smoke, it is nicotine that leads to addiction, he explained. Keeping the substance away from the brain can stymie nicotine's addictive power by preventing smokers from enjoying their cigarettes, Prof Crystal added.
"This looks really terrific if you're a mouse, but they aren't small humans," said Prof Crystal.
The gene therapy delivers the vaccine to the liver using a virus engineered not to be harmful. The gene sequence for the antibodies is inserted into liver cells, which then begin to create antibodies to nicotine.
"The antibody is floating around like Pac-Man in the blood," Crystal said. "If you give the nicotine and the anti-nicotine gobbles it up, it doesn't reach the brain."
Other "smoking vaccines" have been developed that train the immune system to produce antibodies that bind to nicotine -- the same method used against disease.
The challenge has been to produce enough antibodies to stop the drug entering the brain and delivering its pleasurable hit.