Forbes: Quitter's Aid
Kerry A. Dolan, 07.26.04
A nicotine vaccine may help smokers stop for good.
Nearly half a million Americans die from smoking--related illnesses each year, the biggest reversible mortality statistic in the Western world, yet 46 million adults and 3.2 million teenagers in the U.S. continue to puff away. Nicotine is so powerfully addictive--more than heroin, cocaine or speed--that nine out of ten smokers who stop are at it again within a year.
Drug firms have been targeting the habit for years, with mixed results. The most successful approach has been the palliative: products like nicotine patches and gums, now a $630 million category, according to ACNielsen. Patches and gums have shown that they can, by slowly weaning smokers off the drug, double the rate at which smokers quit for good.
Now a more direct approach in the fight against nicotine addiction is emerging: an experimental vaccine to block the nicotine from entering the brain to deliver its pleasurable rush. If it doesn't feel good, smoking may be easier to pass up.
Nicotine floats around the blood like any other foreign antigen, but its molecules are small enough both to slip past the blood-brain barrier and elude the immune system's policing antibody cells. A nicotine vaccine would work like other vaccines, provoking the body into producing targeted antibodies that, in this case, latch onto molecules so they're too big to enter the brain.
Several companies are pursuing nicotine vaccines, including Nabi Biopharmaceuticals in Boca Raton, Fla.; Cytos, a Swiss biotech; Xenova in the U.K.; and Prommune, a small firm in Omaha, Nebr. For now Nabi is furthest along, with its NicVax vaccine. Preliminary quitting rates are due out later this year from its study of 63 smokers who were injected with the vaccine. Earlier animal studies had shown that antibodies to NicVax reduced the amount of nicotine in the brains of immunized animals and moderated nicotine's side effects, such as increased blood pressure.
Nabi's work on a smoker's vaccine dates to 1996, when Ali Fattom, the company's vice president of research, came up with a workable vaccine for Staphylococcus aureus, a leading cause of infection in hospitals. Staph molecules are good at eluding the immune system because they're disguised by an abundant coat of sugars. Fattom's solution was to link the sugars to a larger carrier protein, in this case an inactivated bacteria called Pseudomonas. The immune system spots the combination and produces antibodies that then bind to the staph molecules in the body, preventing infection. (Nabi's staph vaccine is in late-stage trials.)
Fattom figured the same process would work on other elusive molecules, and he set his sights on nicotine. Nabi scientists chemically synthesized nicotine molecules and stuck them onto the Pseudomonas protein. Once injected, the protein-nicotine combo triggers the immune system to create nicotine-specific antibodies. These antibodies bind to the nicotine in a smoker's blood, preventing it from getting to the brain. The antibody-nicotine complex continues to circulate in the blood until the nicotine eventually breaks down.
An early-stage human trial Nabi completed in 2002 proved that nicotine antibodies were still at measurable levels in the blood for 7 to 14 days after one shot. Side effects such as soreness and redness at the injection point cleared up in a few days. "If the vaccine works, it would be a huge addition to the tool kit," says Stephen Rennard, a principal investigator in the ongoing Nabi trial and a professor of medicine at the University of Nebraska College of Medicine.
John Hughes, a smoking-cessation expert and professor of psychiatry at the University of Vermont College of Medicine, is slightly less enthusiastic. "If it can do better than [existing treatments], it would be impressive," says Hughes. "I see it as one more option for smokers who want to quit." |
