Scientists test a new vaccine against addiction to cocaine

The vaccine, called TA-CD, shows promise but could also be dangerous; some of the addicts participating in a study of the vaccine started doing massive amounts of cocaine in hopes of overcoming its effects, according to Thomas R. Kosten, the lead researcher on the study, which was published in the Archives of General Psychiatry in October.

“After the vaccine, doing cocaine was a very disappointing experience for them,” said Kosten, a professor of psychiatry and neuroscience at Baylor College of Medicine in Houston.

Nobody overdosed, but some of them had 10 times more cocaine coursing through their systems than researchers had encountered before, according to Kosten. He said some of the addicts reported to researchers that they had gone broke buying cocaine from multiple drug dealers, hoping to find a variety that would get them high.

Like disease vaccines, TA-CD stimulates a person's immune system to produce antibodies. Of those who received all five vaccine injections, 38 percent reached antibody levels that were high enough to dull the effects of the drug. The antibodies stayed active for eight to 10 weeks after the last shot.

In the high-antibodies group, 53 percent stayed off cocaine more than half the time once they had built up immunity. That compares with 23 percent of those who produced fewer antibodies. The researchers monitored cocaine use through regular urinalysis.

“In this study, immunization did not achieve complete abstinence from cocaine use,” Kosten said. “Previous research has shown, however, that a reduction in use is associated with a significant improvement in cocaine abusers' social functioning and thus is therapeutically meaningful.”

Through newspaper ads, Haney had recruited 15 cocaine-dependent men to participate in her study (only 10 stayed to the end).

Haney, who has been studying pharmacological treatment for cocaine addiction for 15 years, said she was surprised by how effective the medication was in blocking cocaine's effects. In the conclusion of her study, Haney suggested that the vaccine could help protect motivated treatment-seekers from relapse because if they slipped and used some cocaine, they wouldn't get high and trigger the craving for more drugs.

Regarding the ethics of giving laboratory-produced crack cocaine to the men, none of whom was seeking treatment for his addiction at the time of the study, Haney said that the benefits of developing a vaccine outweighed any potential harm. She said scientists have been doing these types of studies — funded by the federal government — for 20 years under safe, controlled conditions. “I sleep well at night because it's unethical not to do well-designed studies,” she said.

A larger six-site clinical trial of the vaccine organized by Kosten is scheduled to start in the spring.

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