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Fall 2010

You'll Get No Kick from Cocaine

Vaccine shows promise in blunting tough-to-beat addiction.

By: Marjorie Centofanti
Date: October 1, 2010

cocaine usage

What if there were a safe and lasting way to block the high that users get from cocaine, no matter what form—injected, snorted, or even the potent inhaled drug called crack? 

That possibility came a bit closer this summer, when Hopkins began trials of a prototype cocaine vaccine with 50 active cocaine users—men and women who say they want to quit. Some 300 will participate nationwide.

Led by Maxine Stitzer and Andrew Tompkins, with the Behavioral Pharmacology Research Unit, the team is one of six nationally to conduct phase II trials of the TA-CD vaccine. Ideally, the vaccinations will jog subjects’ immune systems to create useful antibodies—those able to pick off cocaine molecules before they cross the blood-brain barrier to stimulate dopamine-based reward circuits in the brain.

Stopping cocaine’s effects completely could bring a sea change in recovery strategies, the researchers say. But even if the vaccine merely blunts the high, that might tip the balance enough to make existing tactics more effective.

The studies follow a decade of animal research and then a sentinel inpatient vaccine study of cocaine users. “Even before it appeared in a journal last fall, the results of that inpatient trial caused a stir in the research community,” says Stitzer. “It was the first time a treatment substantially reduced the subjective effects of cocaine. After literally years of seeing negative trials, this would be hard to overlook. 

“That said,” she adds, “we know there are still challenges.” The anti-cocaine antibody levels, for example, fade within a year, making booster shots necessary. In a larger outpatient study, just half of fully inoculated people produced enough antibodies to dull cocaine’s effects.  Still, Tompkins points out, the possibility of helping even that many motivated cocaine users is highly significant for a life-sinking illness that affects millions.

He also takes heart in the potency of the vaccine for those who are affected by it. “It appears to damp down even crack cocaine,” Tompkins says, “which travels the fastest to the brain.”

Unlike other addictive drugs, cocaine has thumbed its nose at 30 years of concerted searching for a medication to stop dependence. The same is true for its amphetamine cousins and the other stimulants. There’s no methadone-equivalent, as exists for heroin or other opioid addictions. Much of the problem, Tompkins says, stems from the stimulants’ intimacy with normal brain circuitry: “That makes it difficult to find an agent that blocks the drugs while leaving important brain function intact.”

In the ongoing trials, it will take several injections of vaccine to get the anti-cocaine antibody titer as high as necessary. The physiology and safety will be under study, but researchers’ eyes will linger longest on the urine tests and written surveys that will flag a hoped-for drop in cocaine use. If the trials are successful, says Stitzer, the vaccine would be a candidate for FDA approval, and then, ideally, tailored to community use.

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