A small trial of an experimental vaccine designed to stop cocaine reaching the brain suggests that it helps reduce the drug鈥檚 use.
Over a 32-week trial involving monthly injections, the urine of seven people given the vaccine was 17 per cent more likely to test negative for cocaine compared with that of three people given a placebo injection, says at Weill Cornell Medical College in New York City. 鈥淭he participants in the trial were all considered severely addicted.鈥�
But this trial was mainly intended to assess the safety of the vaccine, so a larger one will be needed to properly assess its efficacy, he says. So far, the vaccine does appear to be safe, with the only report of an adverse response being in a person given the placebo.
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The vaccine is designed to stimulate the immune system to produce antibodies that bind to cocaine in the bloodstream. When a cocaine molecule is bound to an antibody, it can鈥檛 get through the blood-brain barrier into the brain. Instead, the drug is rapidly degraded, says Kaminsky.
This means people no longer get high when they take the drug, which may be why there was also a 27 per cent drop in reported cravings over the 32 weeks.
The challenge is getting the immune system to produce enough antibodies to mop up all the cocaine molecules. An earlier experimental cocaine vaccine developed by at Baylor College of Medicine in Texas and his colleagues was found in a later-stage trial to produce enough antibodies to have a therapeutic effect in only two-thirds of those given it. US regulators didn鈥檛 approve further trials.
Kaminsky says his team鈥檚 cocaine vaccine, known for now as dAd5GNE, stimulates the production of higher antibody levels than the earlier vaccine. This is achieved by binding a chemical whose structure resembles cocaine to proteins from the outer shell of an adenovirus, one of the viruses that causes the common cold.
The adenovirus proteins act as a so-called adjuvant, stimulating a strong response. 鈥淭hey鈥檙e incredibly immunopotent,鈥� says Kaminsky.
If the vaccine is approved after further trials, he envisages it being offered as an option to people trying to overcome their addiction. 鈥淭here are a lot of people who have been addicted for a long time that are desperate to get off cocaine,鈥� says Kaminsky, who reported the results at a meeting of the American Society of Gene & Cell Therapy in New Orleans, Louisiana, on 16 May.
It is an innovative approach, says Kosten. 鈥淲hile I have not seen this adjuvant used in humans previously, this new combination of vaccine and adjuvant has a good chance of success.鈥� However, giving monthly injections might be impractical, as people who are heavy cocaine users might not turn up regularly, he says.
A drug called mavoglurant has also shown promise for helping people reduce their use of cocaine in a small trial.
