So far, people have tried lots of ways to quit smoking -- from patches to hypnotism to pure willpower. But Dr. Paul Pentel of the Hennepin County Medical Center in Minneapolis is working on an altogether new approach: a nicotinevaccine.
And judging from a study released today, he may be onto something. Pentel and his colleagues have found that the vaccine was able to block the effects of nicotine in experiments with laboratory rats.
They're still several years away from trying the vaccine in humans. But experts say the early results are promising because they show it's possible to prevent nicotine from reaching the brain.
"The idea is a relatively simple one," said Pentel, director of the Tobacco Dependence Clinic at HCMC. "Nicotine acts in the brain to produce addiction. So if it were possible to keep nicotine from getting to the brain, it ought to be possible to reduce the addictiveness of nicotine."
The vaccine, known as NicVax, was initially developed by Pentel and his colleagues at the Minneapolis Medical Research Foundation, the research arm of the Medical Center, and is now produced by a Florida pharmaceutical company, Nabi.
NicVax is, in fact, one of a handful of experimental vaccines that researchers around the world are testing against a number of addictive drugs, including cocaine, according to the National Institute on Drug Abuse.
Dr. Alan Leshner, the institute's director, praised Pentel's study, saying it showed that a vaccine "may be useful for preventing and treating tobacco addiction" by taking the "kick" out of smoking. The institute has helped fund the research with a $600,000 grant.
The goal, said Pentel, is to get the body's immune system to develop antibodies to nicotine, much as a polio vaccine fights a virus. The antibodies would attack the nicotine a smoker inhales before the chemical reached the brain, where it produces its pleasurable effects.
But Pentel cautions that, even if it works, "the vaccine will not be a magic bullet . . . [It] is unlikely to make someone quit smoking if they don't want to quit. The hope is it will make it much easier if they do."
In the animal experiments, Pentel's team gave lab rats the equivalent of two to 10 cigarettes' worth of nicotine and found that the vaccine cut the concentration of nicotine in the brain by two-thirds.
In addition, the vaccine blocked nicotine's effects on the rats' behavior. Once immunized, they no longer experienced increases in blood pressure and physical activity.
So far there have been no side effects, Pentel said. And unlike other types of vaccines, this one doesn't last long.
"It's not like [when] you get immunized for tetanus and you only have to come back ten years later." The effects would probably wear off in a matter of months, he said. But that could be enough to wean smokers from their habits; booster shots could help prevent relapse.
Pentel is reluctant to speculate on how the vaccine might be used until further research is done. He notes, however, that vaccines already have shown promise in experiments with heroin and cocaine. "It's not a new idea; it's 25 years old," he said. "But we're now trying to apply it to the leading preventable cause of death."
If all goes well, testing of the nicotinevaccine in people is scheduled to begin in early 2002, according to the institute..
If it worked, "it would be a wonderful thing," said Dr. Marc Manley, who runs the Center for Tobacco Reduction and Health Improvement at Blue Cross and Blue Shield of Minnesota.
"People would like to have something so we could vaccinate our children and, in effect, make them immune to cigarette advertising," he said. At the same time, he warned, experience shows that medications alone won't solve the problem and that people often need behavioral counseling.
He noted that only 20-30 percent of the people who try to quit smoking succeed, using such stop-smoking medications as nicotine patches, nicotine inhalers and drugs such as Zyban.
Dr. Richard Hurt, director of the Mayo Clinic's Nicotine Dependence Center in Rochester, Minn., called the research "a very creative advance." But he, too, added a word of caution. "We're at the beginning of the beginning when it comes to pharmacotherapy [for] nicotine dependence treatment," he said. "Smokers are looking for a magic cure, and there's not going to be one. This is too complicated a behavior."
Pentel readily agrees. "The most realistic scenario is that this will be one other medication that we can add to [our] repertoire," he said.
Pentel's study, which was published in the journal Pharmacology, Biochemistry and Behavior, was done in collaboration with Hennepin County colleagues Dan Keyler and Yoko Hieda and scientists at Nabi and the University of Houston.
© Copyright 1999 Star Tribune. All rights reserved.
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