Dipali Pathak
713-798-4710
pathak@bcm.edu

HOUSTON -- (Oct. 5, 2009) -- A cocaine vaccine that recruits the immune system to help block the drug's euphoric effects proved effective in 38 percent of subjects who received the vaccine, said a Baylor College of Medicine researcher who led the study.

Q&A with Dr. Kosten

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Text-only Q&A

A consortium of researchers began the work when principal investigator Dr. Thomas R. Kosten, a professor at BCM, was on faculty at Yale University School of Medicine. Kosten and his team evaluated the safety and effectiveness of a novel cocaine vaccine that has been more than 15 years in development. The report appears in the current issue of Archives of General Psychiatry.

Plans to improve cocaine vaccine

"The concept works," said Kosten, "There are lots of ways to engineer it after that to make it work better."

He plans to continue work to improve the vaccine and find better ways to bolster the immune system against the effects of cocaine.

Kosten holds the Jay H. Waggoner Endowed Chair in the Menninger Department of Psychiatry and Behavioral Sciences at BCM. He is also the research director of the Veterans Affairs National Substance Use Disorders Quality Enhancement Research Initiative based at the Michael E. DeBakey Veterans Affairs Medical Center in Houston.

This study took place in one center, the Veterans Affairs Connecticut Healthcare System. Plans for a study of the vaccine in many sites are now under way.

Promising step

"The results of this study represent a promising step toward an effective medical treatment for cocaine addiction," said Dr. Nora Volkow, director of the National Institute on Drug Abuse. "Provided that larger follow-up studies confirm its safety and efficacy, this vaccine would offer a valuable new approach to treating cocaine addiction, for which no FDA-approved medication is currently available."

Kosten is quick to note that the vaccine is not a panacea, but the result shows that a vaccine can work in addictive disease, he said.

"The vaccine provokes the body to make antibodies. These antibodies bind to the cocaine, preventing it from leaving the bloodstream," said Kosten.

The cocaine can be excreted in the liver or kidneys. An enzyme in the blood, cholinesterase, breaks down the cocaine. The fact that this enzyme continually breaks the drug down makes cocaine a better target for vaccines than other addictive drugs.

Effectiveness depends on level of antibody

In the study, 94 subjects who were on methadone were randomized to receive either the vaccine or an inactive medicine, a placebo. Neither they nor the physicians knew who received the vaccine until the study was over. Most subjects smoked crack cocaine. Over 12 weeks, the subject received five injections of either the vaccine or the placebo.

The vaccine's effect depended on the level of antibody achieved. Those who reach high levels of antibodies are more likely to be able to stay cocaine-free.

"That's the biggest problem with this vaccine. It is first generation and it does not create antibodies in everybody," said Kosten. "Twenty-five percent of the people who get the vaccine do not make much antibody response."

Relapse prevention medication

The vaccine can act as a preventive to relapse for those who want to stop taking the drug, Kosten said. It does not completely prevent cocaine cravings, but when the effect of the drug is blocked by the vaccine, people's cravings will diminish.

"This is a relapse prevention medication. If you take cocaine, you won't feel anything," he said.

Others who took part in this research include Drs. Bridget A. Martell and James Poling and registered nurse Ellen Mitchell of Yale University School of Medicine and the Veterans Affairs Connecticut Hospital; and Drs. Frank M. Orson, Roger D. Rossen and Tracie Gardner of Baylor College of Medicine and the Michael E. DeBakey Veterans Affairs Medical Center in Houston.

Funding for this study came from the National Institute of Drug Abuse, the Veterans Affairs Mental Illness Research, Education and Clinic Center in New England, the Veterans Affairs Office of Research and Development/Cooperative Studies Program Career Development Award. Celtic Pharmaceuticals provided vaccine and paid travel fees for consultative services as well as providing a small amount of administrative funds for design and conduct of the study.

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