NicVAX update
For smokers, a shot at quitting
A nicotine vaccine may break the cycle that fuels the habit.
By Regina Nuzzo, Special to The Times
July 17, 2006
The vaccine, called NicVAX, is far from proven technology. But it has shown
promise in early trials even in smokers who had no plans to quit.
In March, the Food and Drug Administration granted NicVAX’s manufacturer,
Nabi Biopharmaceuticals of Boca Raton, Fla., a fast-track application to
help speed the drug’s review process.
Now nine centers across the U.S., including UCLA, are recruiting smokers
for a Phase 2 clinical trial. Initial results of the trial, funded in part
by a recent $4.1-million grant to Nabi from the National Institute on Drug
Abuse at the National Institutes of Health, are expected in mid-2007.
Better quit-smoking therapies are sorely needed to treat today’s smokers,
who appear to smoke more heavily and be more addicted than in the past,
says Elbert Glover, professor of public and community health at the
University of Maryland and head of the Maryland trial. This year, more than
400,000 smokers in the U.S. will die from smoking-related illnesses,
according to the Centers for Disease Control and Prevention. About 70% of
the 49 million adults and 6 million teenagers who smoke in the U.S. say
they would like to quit, and every year about 40% of them try.
Fewer than 3% succeed.
Scientists believe the new vaccine might help smokers who haven’t been able
to quit with other methods.
On their own, nicotine molecules just like those in drugs such as heroin
and cocaine are too small to trigger the body’s immune system, says Dr.
Victor Reus, professor of psychiatry at the UC San Francisco School of
Medicine and head of the San Francisco trial. These molecules slip quickly
and easily from the bloodstream into the brain, where they bind with nerve
receptors and trigger a pleasurable dopamine release.
Thus, to create an effective vaccine, scientists attached nicotine
molecules onto larger proteins. After injection with the vaccine, the
immune system creates antibodies that specifically recognize nicotine. When
a vaccinated smoker takes a drag, these antibodies attack nicotine in the
bloodstream. Bound nicotine molecules, too big to cross the blood-brain
barrier, are eventually eliminated harmlessly by the body.
Antibodies build up slowly, and patients get “six weeks of guilt-free
smoking” after the first injection before they’re instructed to quit, says
Mitchell Nides, a consultant on the Los Angeles trial. “This is not a
cold-turkey approach at all,” he says.
Since the method targets nicotine, not the brain, researchers hope to see
fewer side effects than with other pharmacological tools (see box). The
antibodies could persist for months after injection, and possibly even
longer with a booster shot, so the vaccine might also help guard ex-smokers
against a relapse.
Using antibodies to treat drug abuse isn’t new, Reus says. In the early
1970s, researchers tested monkeys with an experimental vaccine for heroin
addiction. Today, new vaccines are being developed to treat addiction to
heroin, cocaine, PCP and methamphetamine.
Other companies are also developing nicotine vaccines: Cytos Biotechnology
of Zurich, Switzerland, which presented results of a Phase 2 clinical trial
in Europe in May 2005; Xenova Group of Berkshire, England; and Prommune of
Omaha, Neb.
An earlier, smaller test of NicVAX’s safety included active smokers who had
no plans to quit. Even so, results were surprisingly good, says Dorothy
Hatsukami, professor of psychiatry at the University of Minnesota and lead
author on the study’s report. Thirty-eight percent of smokers in a group
that received a higher dose of the vaccine quit smoking for at least a
month, compared with 9% in the placebo group.
Still much remains to be studied. Researchers aren’t certain if the vaccine
is safe for pregnant women. And, for reasons that are still unclear, some
smokers may not develop enough antibodies for the vaccine to be effective.
With the new 300-patient clinical trial, scientists hope to determine what
types of smokers are most likely to benefit from the vaccine.
By some measures, nicotine can be as addictive as heroin or cocaine, says
Saul Shiffman, professor of psychology at the University of Pittsburgh. But
research has shown that nicotine addiction also gains its strength from
dozens of daily habits in a smoker’s life whether a few puffs in morning
traffic or half a pack on the bar stool at night.
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