Vaccine hope for cocaine addicts

Byline: Mark Court

The search for a vaccine to cure cocaine addiction has moved a step closer with work about to start on the second stage of clinical trials.

The work is being carried out by Xenova, the Slough biotechnology company. The vaccine, code-named TA-CD, is understood to be the only product of its type in clinical trials, marking a new approach to the treatment of cocaine addicts, who usually have to rely on counselling and rehabilitation clinics. Cocaine addicts, including many high-profile users in the music and entertainment industries, try hard to overcome their addiction but most relapse, creating huge interest in new treatments. 

Xenova's vaccine, which has already completed phase I clinical trials to show that the drug is safe, is designed to stop addicts receiving a "high" by preventing the cocaine molecule entering the brain.

Cocaine, in common with nicotine, is a very small molecule which, when in the bloodstream, is able to sidestep the brain's protective layer, called the blood-brain barrier, which has evolved to prevent potentially damaging material getting into the brain.

Once there, cocaine interferes with the junctions between nerve cells, producing the high associated with the drug. Cocaine is too small to be recognised by the body's immune system. However, Xenova's TA-CD is seeking to stimulate the immune system to recognise cocaine so that itbecomes swamped by antibodies, making it too large to cross the blood-brain barrier.

Addicts who relapsed would get no pleasure from cocaine. TA-CD is a combination of the cocaine molecule and a large protein that, when injected into the body, is large enough to be recognised by the body's immune system and for antibodies to be generated. Subsequently, if cocaine is taken, these antibodies can recognise the free cocaine molecules in the blood and combine with them to form a complex that is too big to cross the blood-brain barrier.

Xenova is about to begin phase II trials to monitor the effectiveness of the vaccine, before the start of a larger-scale trial, which would preceed an application for regulatory approval for the product.

The company is also working on a vaccine against nicotine addiction. Phase I trials began last September and results are expected by the autumn.