A vaccine shown to block cocaine from entering the brains of drug-addicted mice could offer hope to human addicts struggling to kick their habit.
Addiction medicine specialists have long been limited in their ability to help cocaine addicts because there is no effective medication specifically created for cocaine dependency. Addicts are typically treated instead with behavioral therapies and 12-step programs.
This vaccine goes at the problem from a different perspective: by tapping into the body’s own immune system.
The vaccine is combination of a common cold virus and particles of substance that mimics the molecular composition of cocaine.
In a study released this week, researchers found that mice given the vaccine appear to mount an effective antibody immune response that helps their bodies stop cocaine from actually reaching the brain.
If the vaccine works as well in people as it does in mice, it could become the first treatment of its kind to help cocaine addicts — and perhaps one day, heroin, alcohol and even nicotine addicts as well.
The vaccine study was funded by the National Institute on Drug Abuse (NIDA) in the U.S.
Dr. David Shurtless, the director of the division of Basic Neuroscience and Behavioral Research at NIDA, explains that the vaccine uses an adenovirus, which invades the body easily, that has a chemical attached to it that’s structurally similar to cocaine.
He says researchers led by Dr. Ronald G. Crystal, professor of genetic medicine at Weill Cornell Medical College in New York, tested the vaccine by injecting it into mice that had been trained to be addicted to cocaine.
“By giving this combination, they actually taught the immune system to recognize the structure of cocaine, which wouldn’t naturally happen,” Shurtless explained to CTV’s Canada AM earlier this week.
“So when they injected cocaine into these immunized mice, the antibodies actually recognized the cocaine as a foreign body — as a virus to attack — and engulfed it. And by engulfing it, the molecule becomes very large and is unable to get into the brain, thus preventing it from hijacking the brain’s reward pathways.”
The researchers found that the vaccine reduced the amount of cocaine getting to the brain by 40 per cent. The mice also displayed much less hyperactivity than the non-vaccinated mice after being injected with cocaine, even when given large, repeated doses.
The effects of the vaccine, which was given in three doses, were found to last for at least 13 weeks. The study results are published in the journal, Molecular Therapy.
The vaccine will need to be tested in humans, but the researchers say they are hopeful it will have the same effects in humans as it did in mice.
Shurtless says the vaccine approach is a new one that could one day be used to help treat addictions to other drugs. In fact, he says, a company called Nabi Biopharmaceuticals is working on a product call NicVax, a similar vaccine to treat nicotine addiction.
“It operates in very much the same way as this cocaine vaccine,” Shurtless said. “It’s in Phase 4 clinical trials being tested in smokers. And with any luck, this could be on the market within a few years for treating tobacco addiction.”
He says researchers are also looking into vaccines to help treat heroin addiction and other substance-use disorders.
“We think it’s a very promising approach,” he said.
“If we can prevent the drug from getting into the brain, we can prevent what we call drug abuse relapse where, even after people abstain for a long period of time, even a single use of the drug can lead to this chronic craving and compulsive drug-taking and relapse to addiction.”
Further studies are still needed to see whether blocking the uptake of cocaine in the brain actually helps addicts to recover. Some are warning that blocking the physical addiction won’t address issues of psychological addiction. Others worry the vaccine could lead addicts to try to compensate for the blockade by increasing their drug intake, perhaps leading to overdoses.
Angela Mulholland
CTV