Cocaine vaccine a step closer to human trials

NEW YORK—Researchers at Weill Cornell Medical College have successfully testedtheir novel anti-cocaine vaccine in primates with successful results, bringing the prospect of human clinical trials to a much closer point on the research and development horizon. More specifically, theirstudy, published online by the journal Neuropsychopharmacology, used aradiological technique to demonstrate that the anti-cocaine vaccineprevented the drug from reaching the brain and producing adopamine-induced high.

The study's lead investigator, Dr. RonaldG. Crystal, chairman of the Department of Genetic Medicine at WeillCornell Medical College, offered this analogy: "Thevaccine eats up the cocaine in the blood like a little Pac-man beforeit can reach the brain."

"Webelieve this strategy is a win-win for those individuals, among theestimated 1.4 million cocaine users in the United States, who arecommitted to breaking their addiction to the drug," he added. "Even if aperson who receives the anti-cocaine vaccine falls off the wagon,cocaine will have no effect."

Crystal says he expects to begin human testing of the anti-cocaine vaccine within a year.

Thenovel vaccine Crystal and his colleagues developed combines bits ofthe common cold virus with a particle that mimics the structure ofcocaine. When the vaccine is injected into an animal, its body "sees"the cold virus and mounts an immune response against both the virus andthe cocaine impersonator that is hooked to it.

"The immune system learnsto see cocaine as an intruder," said Crystal. "Once immune cellsare educated to regard cocaine as the enemy, it produces antibodies,from that moment on, against cocaine the moment the drug enters thebody."

Intheir first study in animals, the researchers injected billions oftheir viral concoction into laboratory mice, and found a strong immuneresponse was generated against the vaccine. Also, when the scientistsextracted the antibodies produced by the mice and put them in testtubes, it gobbled up cocaine. They also saw that mice that received boththe vaccine and cocaine were much less hyperactive than untreated micegiven cocaine.

Previousresearch had shown in humans that at least 47 percent of the dopaminetransporter had to be occupied by cocaine in order to produce a drughigh. The researchers found, in vaccinated primates, that cocaineoccupancy of the dopamine receptor was reduced to levels of less than 20percent.

"Thisis a direct demonstration in a large animal, using nuclear medicinetechnology, that we can reduce the amount of cocaine that reaches thebrain sufficiently so that it is below the threshold by which you getthe high," explained Crystal.

Whenthe vaccine is studied in humans, the non-toxic dopamine transportertracer can be used to help study its effectiveness as well, he added.

Theresearchers do not know how often the vaccine needs to be administeredin humans to maintain its anti-cocaine effect. One vaccine lasted 13weeks in mice and seven weeks in non-human primates.

"Ananti-cocaine vaccination will require booster shots in humans, but wedon't know yet how often these booster shots will be needed," acknowledgedCrystal. "I believe that for those people who desperately want to breaktheir addiction, a series of vaccinations will help."

SOURCE: Weill Cornell Medical College news release