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January 04, 2011

Scientists Make Progress on Cocaine Vaccine for Addicts

Researchers have developed a cocaine vaccine that could eventually offer addicts another way to break their habit. The vaccine prevents the drug from stimulating the brain's biochemical reward center.

In 2008, the United Nations estimated there are between 16 million and 38 million so-called "problem drug users" in the world, including people who are addicted to cocaine.

Beyond psychological counseling and support groups, experts say, there is no treatment for cocaine addiction.

Now, U.S. researchers say they have developed a vaccine that may someday help a sizable portion of cocaine addicts kick their habits.

The vaccine, made of proteins from a harmless cold virus and a molecule that mimics cocaine, sequesters the drug and keeps it from reaching the brain's reward center, according Ronald Crystal of the Department of Genetic Medicine at Weill Cornell Medical College in New York.

Crystal led a team of researchers that vaccinated mice and then injected them with cocaine. "We gave it repetitively to the mice, every week.  So, …think of somebody going to a party and having their cocaine once a week and it never touched the mice. So, week one, week two, week three, week four, we keep giving them cocaine; the mice just sit there like you gave them water," he said.

The vaccine's anti-cocaine effects lasted for 12 weeks in the mice experiments. Crystal said it is likely that booster vaccines would be needed to maintain the beneficial effect in a recovering human addict.

At least one other cocaine vaccine is in human trials, but so far studies show it is only about 40 percent effective in suppressing the craving for cocaine.

Crystal says his vaccine appears to be highly effective, at least in mice, because it's combined with a viral particle that the body is highly attuned to.

"Our immune systems react very rapidly and with great vigor toward the viruses, and the cold virus is at the top of that category.  And so by taking an adenovirus that we then ripped it apart, we were actually using pieces of an adenovirus, that's what we hooked the cocaine to," he said.

The work by Crystal and colleagues was funded by the US National Institute on Drug Abuse.

NIDA Director Nora Volkow says the challenge with developing a cocaine vaccine has been getting the immune system to recognize the drug as an invader because the cocaine molecule is so small.   

Volkow says a similar approach using an adenovirus could be used to develop vaccines against other addictive substances, including heroin. "What would be modified is the compound that you go after, because it has a very chemical structure; so a vaccine that works for cocaine will not work for heroin and vice versa," she said.

Vaccines for substances such as cocaine, heroin, alcohol and tobacco could go a long way in helping addicts break their habits.  

They could also help countries deal with the fall-out of addiction, including drug trafficking violence, soaring health costs and lost worker productivity.  

Cornell-Weill researcher Ronald Crystal thinks human trials of the vaccine could begin in one to two years.    

An article describing the cocaine vaccine is published in the journal Molecular Therapy.