Scientists test vaccine to help smokers beat the habit

Scientists have developed an anti-addiction vaccine that could help smokers to give up cigarettes and cocaine users to kick their habit, researchers told the Science Festival at Salford University yesterday.

The vaccine has already passed safety trials on patients, and doctors are planning more detailed tests later this month to see how good it is at overcoming drug addiction.

Campbell Bunce, a scientist at the Cambridge biotechnology company Xenova, said the vaccine worked by preventing nicotine or cocaine from entering the brain where they triggered further cravings.

The vaccine stimulates the body's immune defences to produce antibodies that bind to nicotine or cocaine in a person's bloodstream, thereby preventing the much larger molecular complex from crossing the vital membrane that separates the bloodstream from the brain.

"The whole process of getting nicotine and cocaine into the brain is the key to the reinforcement of the drug-taking habit," Dr Bunce told the British Association for the Advancement of Science's annual festival. "So if we can reduce or prevent the entry of nicotine or cocaine into the brain through these antibodies then we'll reduce the desire of the addicts to take their substance of abuse," he said.

"Exclusion from the brain will reduce or prevent the feeling of euphoria which normally reinforces the drug-taking habit. A reduction or absence of this trigger to smoke another cigarette, for example, should have an impact on overall behaviour resulting in a reduced desire to smoke.

"If smokers who have given up find themselves at a party, hopefully the presence of antibodies will prevent the usual hit they experience when they smoke and the desire to have another cigarette will be significantly blunted," he said.

A vaccine works by stimulating the immune system to attack invading viruses or bacteria, but molecules such as nicotine or cocaine are too small for the antibodies to recognise. The trick is to produce harmless proteins that can bind to nicotine or cocaine to form a larger substance that the immune system's antibodies can identify. This is the principle behind anti-addiction vaccines, Dr Bunce said.

"So far, all these vaccines have proven safe in man and can induce cocaine or nicotine-specific antibodies. The next steps ... is to progress with efficacy trials in humans to establish whether this strategy will work," he said.

Initial trials with Xenova's anti-cocaine vaccine suggest that addicts will benefit from the approach. "There were comments along the lines of they had a reduced feeling of euphoria," Dr Bunce said.

"They are also unlikely to reduce anxiety or help depression that is associated with withdrawal symptoms. We feel antibodies will be most useful in preventing relapse."

* A vaccine against a range of "auto-destruct" diseases such as arthritis, asthma and diabetes has been approved for clinical trials in Britain after a successful series of laboratory tests. Scientists at Bristol University said the vaccine was based on a protein found in diarrhoea bacteria, which seems to calm down auto-immune reactions, when the body's antibodies attack its own tissues.