The vaccine is poised to move quickly into human trials
Researchers from The Scripps Research Institute, Weill Cornell Medical College, and Cornell University have produced a long-lasting anti-cocaine immunity in mice by giving them a unique vaccine that combines bits of the common cold virus with a particle that mimics cocaine.
In their study, published January 4, 2011, in the advanced online edition of Molecular Therapy, the researchers say this novel strategy might be the first to offer cocaine addicts a fairly simple way to break and reverse their habit. The approach could also be useful in treating other addictions, such as to nicotine, heroin, and methamphetamine.
"Our very dramatic data shows that we can protect mice against the effects of cocaine, and we think this approach could be very promising in fighting addiction in humans," says the study's lead investigator, Ronald G. Crystal, chairman and professor of genetic medicine at Weill Cornell Medical College.
"The vaccine suppresses the stimulant effects of the drug," said Scripps Research Professor Kim Janda, a co-author of the paper and a pioneer in the field of developing vaccines against addictive drugs such as cocaine. "Unlike other types of treatment, a vaccine such as this one does not interfere with the neurological targets of the drug, but instead blocks cocaine from ever reaching the brain in the first place."
In the new study, the vaccine effect lasted for at least 13 weeks, the longest time point evaluated in such an approach. Since the vaccine likely will not require multiple expensive infusions, the researchers hope that it can move quickly into human trials.
Clinically, this sort of therapy could be given to people in treatment programs to aid in their recovery. And, like most other types of treatment, it will only be useful for those who want the help.
"This vaccine would be most applicable for addicts who are who are interested in getting off the drug," said Janda, the Eli R. Callaway Jr. Chair in Chemistry and a member of the Skaggs Institute for Chemical Biology at Scripps Research. "In essence we view such vaccines as 'immuno-helpers' for treating substance abuse, and, in the case at hand, it might prove to be extremely useful for crack addicts whose relapse rate is exceedingly high."
According to the latest statistics available from National Institutes of Health (NIH) National Institute on Drug Abuse (NIDA) in 2008 5.3 million Americans age 12 and older had abused cocaine in any form and 1.1 million had abused crack at least once in the year prior to being surveyed.
Cocaine, derived from the leaf of the Erythroxylaceae coca plant, is a highly potent drug that, as a salt, is either snorted or dissolved in water and injected directly into the bloodstream. The salt is also often neutralized to make an insoluble "free-base" form that is smoked.
Once ingested in the bloodstream, the drug crosses the blood-brain barrier and accumulates rapidly in the brain. "The brain levels rise very rapidly once cocaine is taken into the system," said Janda.
Moreover, the cocaine builds up in parts of the brain reward systems such as the nucleus accumbens. There, the cocaine molecules interfere with the normal regulation of dopamine by binding to dopamine transporters and blocking them from recycling the neurotransmitter.
This leads to the build-up of dopamine in the nucleus accumbens, which produces a euphoric feeling in the user-a quick rush that hits seconds after taking the drug and lasts several minutes. The psychological effect of this immediate reward is the basis for drug seeking in users. Compulsive users-addicts-will keep a perceived desire for the effect that will many times confound a recovering addict's best efforts to stay clean.
There is a common report among intravenous drug addicts that their first injection-that first snort of coke, shot of heroin, or puff of crack-produced the greatest feeling they had ever experienced. Many will also tell you that they too often spent their money, health, family, friends, and lives to try to get that feeling back.