About 41 percent of smokers try to quit each year, but less than 5 percent of do-it-yourself quitters can stay off cigarettes for three months to a year.
Nicotine vaccine may help smokers
By Deane Morrison
November 17, 2005
The inimitable Mark Twain once said that quitting smoking was the easiest thing in the world because he'd done it thousands of time. So, too, have plenty of modern-day puffers. Surveys show that about 41 percent of smokers try to quit each year, but less than 5 percent of do-it-yourself quitters can stay off cigarettes for three months to a year. More than 45 million Americans smoke, and deaths from lung cancer continue to outnumber deaths from the other five most common cancers combined.
But what if there were a vaccine targeting nicotine, the addictive chemical in tobacco smoke? A new study led by the University's Dorothy Hatsukami shows that a vaccine called NicVAX is safe and well tolerated. The research was not aimed at determining whether the vaccine was effective against smoking, but some evidence for such an effect emerged from the data.
Hatsukami, a professor of psychiatry and psychology, presented the work last week at a meeting of the American Association for Cancer Research's 4th annual Frontiers in Cancer Prevention Research meeting in Baltimore. The study involved 63 subjects at three sites: the University, the University of Wisconsin, and the University of Nebraska. It was funded by the National Institute of Drug Abuse and Nabi Biopharmaceuticals, manufacturers of NicVAX.
The research was not aimed at determining whether the vaccine was effective against smoking, but some evidence for such an effect emerged from the data.
In the study, subjects were given injections of the vaccine plus booster shots one month, two months, and six months later. Each person's shots contained one of three doses of the vaccine or a placebo. The vaccine contained molecules of nicotine attached to a protein "carrier." In response, the subjects' bodies produced antibodies that recognized and attached to nicotine that had entered the bloodstream post-smoking. The antibodies worked by creating nicotine-antibody complexes that were too big to pass through the blood-brain barrier; thus, less nicotine was able to get into the brain.
The researchers found several encouraging results. For one, the higher the vaccine dose, the more antibodies against nicotine the person's body produced. The vaccine produced no measurable withdrawal symptoms and didn't lead smokers to light up more often to compensate for the lost nicotine supply to their brains. And those receiving the highest dose were more likely to abstain from smoking for 30 days than other subjects.
"What's great is that this medication targets nicotine itself and doesn't affect brain function," says Hatsukami. "That means fewer side effects, and, because of the way it is delivered, the cost may be lower and compliance may be better. There's no need to take medications every day--a periodic booster shot would be all that's needed. There is a lot of hope for a nicotine vaccine, but there is no miracle drug."
The reason for the vaccine's success probably rests in the reduced amount of nicotine entering the brain and the slowed delivery of nicotine to the brain. The speed at which a drug enters the brain is important in addiction, says Hatsukami. That's why products that deliver a slow, steady supply of nicotine, such as the patch, would not cause addiction. Besides speed of entry into the brain, the amount of nicotine reaching the brain is a factor in determining the drug's addictive potential and subsequent smoking behavior, she says. With the nicotine vaccine, smokers don't experience a sudden "rush" of nicotine that may be associated with pleasurable effects.
The vaccine will undergo further clinical trials to determine whether higher antibody levels can be sustained for longer periods and to see how the vaccine works on smokers who want to quit, Hatsukami says. If successful, a vaccine would be just one tool among many available to smokers, and any good tool must work on more than one level.
"Smoking is more than a response to nicotine--there are also behavioral components," says Hatsukami. "There must be behavioral components to any treatment."