First Cocaine Vaccine Being Tested in Humans

From the WebMD Archives

March 31, 2000 (Atlanta) -- An experimental vaccine to help cocaine users overcome their habit is currently being tested in humans. If it fulfills its promise, the vaccine, called TA-CD, could offer hope to millions of cocaine users who relapse, despite the desire to quit.

"TA-CD offers the potential for a completely new and highly viable approach to a very serious problem for which there are no alternative therapies," principal investigator Thomas Kosten, MD, says in a prepared statement.

"The White House's Office of National Drug Control Policy estimates that there are 3.6 million Americans who use cocaine [regularly]," Frank Vocci, PhD, tells WebMD. "That is about 2% of the U.S. adult population ? in need of treatment." Vocci is director of the Division of Treatment, Research, and Development at the National Institute on Drug Abuse (NIDA), the organization funding the Kosten study.

Kosten, a professor of psychiatry at Yale, will test TA-CD on 20 individuals, in part to determine dosage. Kosten explains that the goal of this study is to give the vaccine more regularly initially, so that levels of antibody, substances that attack foreign objects in the body, can be increased.

In his initial cocaine vaccine study, Kosten established that the vaccine was effective in producing antibodies that specifically attack cocaine; he determined that the antibodies remained circulating in the bloodstream for, at most, a year. "The results of the first study are simply that we did find antibodies," says Kosten. "[T]he higher the dose of the vaccination, the higher the level of antibodies we got. And there didn't appear to be any safety issues involved."

The vaccine works by inducing the body to create antibodies to cocaine. If a person uses the drug after being vaccinated, the antibodies would bind to the cocaine molecules and keep them from entering the brain and producing a high. The vaccine, however, does nothing to control cravings; in theory, it would be used with other forms of therapy to help patients stay clean.

"[E]ven though [cocaine] is a foreign object to the body, it [is cleared from the body] too fast for the body to recognize and [the body] doesn't have time to make antibodies against it," Kathleen Kantak, PhD, tells WebMD. She explains that when the vaccine attaches to the cocaine, "the immune system kicks in and starts making antibodies that specifically recognize that one foreign component ? which happens to be cocaine. And these antibodies are very long-lasting and circulate in the bloodstream. ? So when a person takes cocaine, before it gets into the brain, it has to get into the [bloodstream, and] these antibodies will recognize and bind to the cocaine, preventing its entry into the brain. If you slow down or reduce the amount of cocaine that gets into the brain, you are going to blunt or block its ability to [produce a 'high']."

Kantak, a professor of psychology at Boston University, paved the way for Kosten's trial by investigating the effects of TA-CD on rodents. She found that vaccinated rodents stopped self-administering cocaine, even when the doses were six times higher than what they were used to. In other words, the vaccine blunted the effect of cocaine even at very high doses. "It is more of a deterrent because if [a user] happens to take it, they won't get the usual effect. At some point, they are going to be able to find a dose of cocaine that will overcome the antibody, but it would be very cost-prohibitive," she says.

Vocci says that NIDA is funding three different cocaine vaccine trials, including Kosten's, "to the tune of $1 million a year." Kosten's is the only one that is being conducted in humans. One of the other vaccines, being developed at the Scripps Research Institute in La Jolla, Calif., works on the same principle as TA-CD. The third, being developed at the University of Cincinnati, also acts via antibodies, although it works in a slightly different way.

There is also a fourth vaccine in the pipeline, being developed at Columbia University, that works on an altogether different principle called catalytic antibody. "What this would do is increase the conversion of cocaine into an inactive substance," says Vocci. "By [breaking down] cocaine in the bloodstream, the vaccine would stop the drug before it has a chance to enter the brain."

While Kosten's vaccine is the one farthest along in development, Kosten and Vocci both agree that it will be at least several years before it is commercially available. In the meantime, questions about its efficacy in humans are still unanswered.

Vocci explains that we have yet to see whether the vaccine will actually work to stop people from using cocaine, even if it does what it should do. He says that some people still take drugs even when they are not experiencing the high. Even so, Kosten says that he is optimistic that the vaccine can help users stay away from cocaine.