In the growing market of pharmacological drug development, a new cocaine vaccine may be another success story for a clinical researcher at Yale.

Dr. Thomas Kosten, a professor of psychiatry at the School of Medicine, led a recent research project aimed at finding a treatment for the estimated three million cocaine abusers in the United States. Behind marijuana, cocaine is the most abused illegal drug.

In his most recent clinical trial, the cocaine vaccine, designated TA-CD, was given to eight patients. Of the eight, six reported using cocaine only once or twice during six months of follow-up treatment.

“I’ve seen lots of other medications that haven’t done anything, so this success was a thrill,” Kosten said.

He added that this trial, part of the second phase of clinical testing, was focused more on the vaccine’s overall efficacy than precise dosages or the drug’s effectiveness for patients with varying levels of addiction.

“We know [the vaccine] makes antibodies, and we know it’s not toxic, and now it’s time to do the next set of studies,” Kosten said.

The initial results indicate that the vaccine is effective for up to a year, with anti-cocaine antibodies appearing after only the second injection.

So far, fewer than 50 patients have used the vaccine in clinical trials, a number Kosten said is “relatively small.”

But Kosten anticipates doing more studies in conjunction with Xenova Pharmaceuticals — the England-based biopharmaceutical company that is developing the vaccine — beginning with 10 to 20 subjects, with up to 300 patients being the year-end goal.

The vaccine works by producing cocaine antibodies just like the ones found naturally in the body. Cocaine binds to these auxiliary antibodies in the bloodstream and stays there, rather than traveling to the heart or the brain, where it can severely affect delicate cellular processes.

This quarantining of the narcotic all but eliminates the euphoric rush associated with the drug’s use. Enzymes then breakdown the cocaine while it is in the bloodstream and flush it from the system.

But Kosten added that this treatment will probably only work for those abusers who are committed to quitting because a higher intake of cocaine can overwhelm the auxiliary antibodies.

Cocaine, even when taken in a small amount, elicits an extreme craving for more of the drug. The hope is that with this vaccine, this effect can be subsided. If a patient relapses, his drug use would be limited to an isolated occasion, as the vaccine would eliminate his temptation to binge.

As far as the development of other vaccines for other drugs, “heroin has effective treatments with methadone and naltrexone, so there’s no real need for a vaccine,” Kosten said. “But whether a vaccine would be helpful in other things that don’t have any effective pharmacological therapies is an interesting question.”

Xenova is also involved in other studies looking at possibilities such as a nicotine vaccine, Kosten said.