Vaccine to help smokers stop

By STEVE CONNOR

Scientists have developed an anti-addiction vaccine that could help smokers to give up cigarettes and cocaine users to kick their habit.

Researchers have told a science festival at Salford University that the vaccine has already passed safety trials on patients and doctors are planning a further set of more detailed tests this month to find how good it is at overcoming drug addiction.

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

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 Salford festival, run by the British Association for the Advancement of Science.

"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.

"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."

Normally a vaccine works by stimulating the immune system to launch an attack on invading viruses or bacteria, but molecules such as nicotine or cocaine are too small for the system's 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.

"So far, all these vaccines have proven safe in man and can induce cocaine or nicotine-specific antibodies," Dr Bunce said.

"The next step for these vaccines is to progress with efficacy trials in humans to establish whether this strategy will actually work to help prevent addicts taking these harmful drugs."

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

However, the scientist emphasised that the vaccine would work only if addicts and smokers really wanted to give up because of the powerful pull caused by drug addiction.

The vaccine was also unlikely to reduce anxiety or help depression that was associated with withdrawal symptoms. "We feel antibodies will be most useful in preventing relapse," Dr Bunce said.



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How it works: The vaccine produces antibodies that bind to nicotine or cocaine in the bloodstream.

The new combined molecule cannot cross into the brain.

This reduces the euphoria from smoking and the craving for more nicotine or cocaine.