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Cocaine vaccine shows promise

October 5, 2009 |  1:00 pm

Cocaine A vaccine to treat cocaine dependence yielded good results in a phase-2 clinical trial and will be tested next year in a larger study, researchers reported today.

The cocaine vaccine is not intended to prevent addiction but instead is designed for use with other treatments, such as behavioral therapy, to assist people in recovery. The vaccine is among a number of research projects relying on similar technology to treat nicotine, heroin and methamphetamine addiction.

Cocaine is comprised of tiny molecules that sneak across the body’s blood-brain barrier before the immune system recognizes the substance as foreign. By attaching cocaine-like molecules to a larger protein, the vaccine circumvents that problem and allows the immune system to recognize the protein and its cargo. If a sufficient level of antibodies is created through repeated vaccine injections, those antibodies will disable the addictive drug before it enters the brain, causes euphoria and triggers the cascade of brain chemicals that lead to drug cravings.

In the current study, researchers enrolled 115 cocaine-dependent people in a 24-week trial. Half of the individuals received five injections of the experimental TA-CD vaccine (which stands for therapy for addiction-cocaine addiction) over 12 weeks while the other half received placebo injections. The participants’ urine was tested three times per week over the course of the study. The vaccine produced a large enough antibody response to reduce cocaine use in 38% of the 55 addicted individuals who received all five injections. There were no serious side effects.

The study is published in the Archives of General Psychiatry.

“The antibodies slow cocaine’s entry into the brain. And because it is slowed down so much, the drug isn’t reinforcing any more,” said Dr. Thomas Kosten, a psychiatrist at Baylor College of Medicine and lead author of the study. "The most promising thing we found is that once we got those cocaine antibody levels up, they were more effective than we thought they were going to be. The part that we did expect, but that was still disappointing, is about 20% of people don't make much of an antibody response."

About 300 cocaine-dependent individuals will be enrolled in a study beginning in January to further test the vaccine, Kosten said. The vaccine approach is intended for use in people who desire to quit using, said Berma M. Kinsey, a research chemist at Baylor who has worked on the vaccine. It is not meant for preventing addictions from forming in the first place or for people who don't want to quit.

"It's for people who are motivated to get off drugs," she said. "It's not a cure-all."

-- Shari Roan

Photo credit: Guillermo Arias  /  AP