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A Drug to End Drug Addiction
Jan. 09, 2008 By HILARY HYLTON

What if science made a pill to protect us from addiction ? keeping us from smoking cigarettes, getting fat or abusing drugs and alcohol? According to encouraging results from several lines of study, it seems that day may be closer than we thought. Researchers in labs around the world are now developing vaccines (not a pill, but an injection) to inoculate people against dangerously addictive substances such as cocaine, heroin and methamphetamine. Within "one to 10 years, and closer to one year," says Dr. Frank Vocci, director of treatment research and development at the National Institute of Drug Abuse (NIDA), scientists may produce a vaccine against cocaine ? one of the more promising areas of research ? that can potentially help millions of addicts, two million in the U.S. alone.

One such vaccine, known as TA-CD (for "therapy for addiction ? cocaine addiction"), is being developed by husband-and-wife team Dr. Thomas Kosten, a psychiatry professor, and Therese Kosten, a neuroscientist and psychologist, at Baylor College of Medicine in Texas. TA-CD has had success in early clinical trials: Now under review, a blinded, placebo-controlled study of 114 subjects showed that compared with the placebo group, people who received the vaccine were twice as likely to reduce their cocaine use by at least 50%. The Kostens are currently seeking approval from the Food and Drug Administration to go ahead with a 300-person, six-city clinical trial that may well be the final step toward federal approval of the vaccine.

"This is a major contribution," says Dr. Peter Cohen, a Georgetown University law professor and physician who heads up the District of Columbia Medical Society's physician health committee, which works to rehabilitate drug-addicted doctors. "Addiction is a medical problem that needs to be treated as a medical problem."

Unlike traditional anti-addiction approaches, such as 12-step programs, psychotherapy and older medications like methadone for heroin addicts or the nausea-inducing Antabuse for alcoholics, vaccines like TA-CD prevent the addictive substance from ever reaching the user's brain ? that is, they inhibit the addictive cycle rather than respond to it. The goal is to eliminate the chemical cascade that results in the euphoric "high," which, in turn, sparks addiction ? what comedian George Carlin once described this way: "What does cocaine make you feel like? It makes you feel like having more cocaine."

While most foreign substances in the body trigger an immune-system defense, many illegal drugs, like cocaine, fail to do so because their molecules are too small; they slip into the brain unnoticed and unchallenged. But by attaching them to larger proteins ? in the case of TA-CD, an inactivated cholera protein that has been widely tested and is unlikely to cause side effects, according to researchers ? the immune system is prompted to create antibodies to both the larger protein and the piggybacked drug. The next time the user takes cocaine by itself, the body mounts an automatic defense: Antibodies attach onto the cocaine molecules, which are then broken down by enzymes in the bloodstream. "It's just like a big sponge for cocaine in the bloodstream," Thomas Kosten says.

TA-CD has been over a decade in the making, but the science behind it goes back much further. In the 1950s, researchers developed a vaccine to block fatal overdoses of the heart drug digitalis. In the 1970s University of Chicago researchers prompted monkeys to develop antibodies to heroin by attaching molecules of the drug to a protein from cow's blood. It was this model on which Kosten, who became interested in solving addiction as a medical student at Cornell, based TA-CD. Using the cholera bacterium as a vector is a crucial tweak in design; it allows the cocaine vaccine to sidestep the potential viral syndrome associated with other vaccines, such as Cytos's experimental anti-nicotine vaccine, which is delivered via virus, Kosten says. And because cocaine addiction is most severe in Western countries where cholera is not a threat and where the cholera vaccine is not widely administered, most people do not yet have natural immunity. "Most Americans don't have antibodies to cholera," Kosten says.

That may be a boon to many of the 22 million drug abusers and addicts in the U.S. Although it's difficult to put a price tag on the total impact of drug abuse, NIDA estimates it costs the U.S. $484 billion a year in health care costs, lost earnings, crime and accidents. Complicating the problem, addicts tend to abuse more than one substance at a time ? two-thirds of cocaine addicts also use alcohol, for example ? a potentially lethal combination that may be increasing in popularity. A 2006 University of Florida study found that deaths from cocaine overdose, which often involved alcohol, increased in Florida from 150 a year in 2000 to 300 in 2005. Researchers hope that addiction vaccines may someday help to reverse those trends, not only through treatment of the addicted, but also by immunizing children from addiction early on. "Addictions," Kosten notes, "are diseases of the young."

TA-CD is currently designed as a therapeutic drug, however, not a preventive, says Kosten. For people struggling to overcome addiction or avoid relapse, the vaccine can reduce the rate of uptake of cocaine and slow the high. Even still, determined users can thwart the vaccine by taking more cocaine than their immune response can handle. The regimen also requires commitment, involving as many as five shots in three months, plus boosters every two months thereafter. "You have to want to quit. The addict has to want to stop" for the vaccine to work, says NIDA's Vocci.

Meanwhile cocaine use continues to rise in other countries, particularly in Europe, where Kosten consults on similar vaccine research. He is also working on a methamphetamine vaccine in the U.S., and a heroin vaccine in China, where increasing heroin use has been linked to skyrocketing rates of AIDS and hepatitis. Unlike the vaccine against cocaine, the heroin vaccine faces a tricky complication: It may interfere with other important treatments. If its protection extends to other opiates, for example, it would prevent patients from responding to medically necessary drugs like morphine. The same potential concern applies to nicotine vaccines that may block normal nerve transmissions involving nicotinic receptors in the brain, which play a role in muscle movement, Cohen says.

As complicated as the puzzle of addiction may be, Kosten believes that the 21st-century war against drug abuse can be waged as successfully as last century's global fight against infectious disease. It may not be a magic pill, but Kosten hopes the TA-CD vaccine will be the first step along the road to recovery for many addicts.
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