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With funding for tobacco treatment studies on the upswing in recent years, researchers are learning even more about tobacco addiction and finding new strategies that may increase quitting attempts and, ultimately, quit rates.
"Within the next few years, we'll have new products and more data on how smokers respond to various cessation medications," says David Gonzales, PhD, co-director of the Smoking Cessation Center at Oregon Health and Science University in Portland. "The increased attention on smoking cessation created by the expected media coverage for the new medications can create a great opportunity for physicians to talk with all their smoking patients about cessation on a broad scale."
SMOKING CESSATION DRUG PIPELINE
At least three new pharmacotherapies are currently in the pipeline—including two oral medications and a much anticipated nicotine vaccine.
Rimonabant (Acomplia, Sanofi-Aventis), a novel cannabinoid receptor blocker, entered the Food and Drug Administration (FDA) approval process in June. It could be used to treat both obesity and smoking cessation (DOC News, September 2005). Approval is anticipated by spring 2006, researchers say.
In large-scale clinical trials, rimonabant curbed both food and nicotine cravings. In one smoking cessation trial presented at the 2004 American College of Cardiology meeting, 800 men and women who smoked an average 23 cigarettes per day were enrolled for the 10-week study. The goal was no smoking for at least 4 consecutive weeks. Of those who completed the study, 36% who received a 20-mg dose of rimonabant were able to meet the goal of 4-week smoking abstinence, compared with about 20% of the smokers receiving placebo. Those in the placebo group gained an average 6.6 lb, compared with 1.5 lb for the rimonabant group.
Rimonabant also was shown to reduce the risk of metabolic syndrome independently of weight loss and smoking cessation among over-weight adults, says Gonzales, who was involved in the research. Metabolic syndrome is a cluster of signs and symptoms, including high blood pressure, glucose intolerance, dyslipidemia, and a large waist size.
"There are really three potential avenues for working with patients on this drug," he says. "For example, if you have a smoker who is obese and also at risk for developing diabetes, you'd have potential positive effects on all three conditions."
The weight-loss effects of rimonabant also may increase motivation to quit.
"Many people gain weight when they quit [tobacco], and that can be an impediment to being successful long-term or even making any attempt to quit," says Stephanie O'Malley, PhD, professor of psychiatry and director of the Substance Abuse Research Division at Yale School of Medicine.
O'Malley's team also is investigating a compound that may help smokers quit without gaining weight when combined with nicotine replacement therapy. This opiate agonist, naltrexone, is currently used for alcohol and drug treatment.
Pfizer is expected to seek approval soon for its novel drug varenicline, a selective nicotinic receptor partial agonist that suppresses nicotine withdrawal symptoms.
According to data presented at the U.K. National Smoking Cessation Conference in London in June, smokers taking 1 mg dosages of varenicline twice daily had higher continuous quit rates at 7 weeks (48%) than those taking bupropion (Zyban, GlaxoSmithKline) (33%) or placebo (17%). That study included more than 500 smokers.
IMMUNIZING AGAINST NICOTINE
Nicotine vaccines also look promising, although their availability is still 5–6 years away, says Frank Vocci, PhD, director of the National Institute on Drug Abuse's Division of Pharmacotherapies and Medical Consequences of Drug Abuse.
At least three companies—including Cytos Biotechnology in Switzerland, Xenova in Britain, and Nabi Biopharmaceuticals in Florida—have variations of a nicotine vaccine in the works.
All function by triggering the patient's immune system to produce antibodies that bind to nicotine, making the molecules too large to cross the blood-brain barrier. In effect, that would eliminate the nicotine-induced "rush" believed to be the main physiological reason tobacco users become addicted and have high relapse rates.
Cytos reported findings from the largest clinical study to date at the American Society of Clinical Oncology meeting in June. That trial included 341 smokers. Two-thirds received five doses of the vaccine, at varying doses, over 4 months. The other third received placebo. All participants received cessation counseling. The data indicated 40% of smokers receiving the vaccine quit smoking for nearly 6 months of follow-up. The highest quit rate (57%) was associated with the highest antibody response. Interestingly, 31% of the placebo recipients also quit smoking during the 6 months.
In a 2004 press release, Nabi reported a 33% quit rate in smokers receiving its vaccine at the highest dosage level, compared with a 9% quit rate in the placebo group. The first phase II clinical trial included 68 patients.
"Conceptually, it's a very promising line of research," says
Michael Fiore, MD, director of the Center for Tobacco Research and
Intervention at University of Wisconsin Medical School. "But for now, we
shouldn't forget that we've got plenty of evidence-based treatments to use
today" ("Nixing Nicotine With Novel Combination Therapies,"
see page 11). 
Footnotes
For guidance on tobacco cessation counseling and prescribing nicotine replacement therapies and bupropion, see "A HowTo Guide for Implementing the Public Health Service Clinical Practice Guideline," available at www.surgeongeneral.gov/tobacco/clinpack.html.
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