Smoking vaccine on horizon

Smokers soon may be able to quit by flipping a switch - inside their own bodies.

Scientists are discovering how to manipulate our natural responses to nicotine, using genetic discoveries to turn off the craving for the powerful drug.

"As a scientist, I don't leap to such wild claims, but that's what we're working toward," says Dr Edward Sellers of the University of Toronto.

For now, researchers have developed a pill that they say reduces a person's desire to smoke, and others are working on a vaccine to do the same thing.

During genetic research on drug addiction, Sellers and his colleagues at the Canadian university discovered that people were less likely to become addicted to nicotine if they lacked an enzyme that breaks down the drug in the body.

If the body can't break down nicotine, it stays in the system longer. That reduces the craving to get more nicotine by smoking more cigarettes.

The scientists began searching for a substance that would mimic the natural enzyme deficiency. After testing more than 200 compounds, they discovered that methoxsalen, a drug used to treat some skin disorders, prevents the breakdown of nicotine.

In a test, 17 smokers were given nicotine orally along with methoxsalen. Those who got high levels of methoxsalen reported a reduced desire to smoke.

A 'Eureka!' moment

Sellers called the discovery of the new therapy "tremendously exciting."

"It doesn't happen very often in one's scientific career that you can find an approach for such a problem that is right up there at the top in terms of a public-health issue," he says. "It was one of those 'Eureka!' moments."

The next step for the methoxsalen pill is large-scale safety testing. Sellers says he believes a stop-smoking pill could be on the market in three to five years.

Other researchers are headed for the same goal, but in the opposite direction: They're developing methods to stop smoking by keeping nicotine from reaching the brain.

Keep nicotine out of the brain, they say, and you stop the craving for the pleasurable sensations it provides those who are addicted to it.

Again, the breakthrough came from genetic research on drug addiction. Scientists discovered that, by combining a nicotine molecule with other molecules in the body, they could stimulate the production of antibodies that keep nicotine out of the brain.

It's the same natural defence the body uses to kill off viruses that cause illness, such as the cold or flu.

And it means that, one day soon, smokers might be able to get a shot to ward off tobacco dependence, much as we now get shots to prevent the flu.

"I think there is no question that this will lead to new approaches to treatment," says Paul Pentel, director of the tobacco dependence clinic at Hennepin County Medical Centre and a lead researcher on the vaccine project.

Blocking nicotine to the brain

In experiments with laboratory rats, Pentel says, a vaccination - which the researchers call NicVAX - reduced the level of nicotine in the brain by up to two-thirds.

"The most important number is the reduction of nicotine in the brain," Pentel says. "The brain is where nicotine produces its addictive effects."

It's unlikely that a pill or a shot alone will keep a smoker off the weed, although experts believe they could play an important role.

"One of the lessons we've learned with all addictive drugs is that medications can be very effective, but by no means are they enough," Pentel says. "Counseling and behavioural treatment with medication works much better than medication alone."

But are smokers ready to take their medicine? Interviews with a half-dozen smokers found little enthusiasm for the new remedies.

"I'm against taking any kind of drugs," says Gail Symon, 67, a smoker for 52 years. "I even avoid taking a pill for a headache."

Juliet Kyese, 18, says she's been smoking for five years and has tried to quit several times. Still, she's not sure whether she would sign up for a no-smoking pill.

"It really depends on how much it would cost," she says. "If it's more expensive than smoking, then probably not."

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