Ten weeks after rejecting Sanofi's application to market Acomplia (rimonabant) as a smoking-cessation aid, the U.S. Food and Drug Administration on May 11th approved the first new prescription drug for smoking cessation in nearly a decade.

The drug, varenicline, will be marketed by Pfizer as Chantix, and was shown in clinical trials to help more than one in five smokers kick the habit. Varenicline was approved in six months rather than the usual 10 because of its demonstrated effectiveness.

The FDA is believed to have informed Sanofi that it would have to conduct a new clinical trial of Acomplia before it would receive further consideration as a smoking cessation aid. Sanofi has not said whether it intends to conduct such a trial.

Varenicline latches on to the same receptors in the brain that nicotine binds to when inhaled in cigarette smoke, cutting the pleasure of smoking and reducing the withdrawal symptoms.

Most other smoking-cessation aids are nicotine-replacement therapies, sold by prescription or over the counter in gum, patch, lozenge, nasal spray or inhaler form.

The last smoking-cessation aid approved by the FDA that was nicotine free was bupropion, an antidepressant already sold as Wellbutrin but approved by the FDA in 1997 as an anti-smoking drug and rebranded for that purpose as Zyban.

"In the clinical trials, smokers on Chantix had four times greater odds of quitting smoking, versus those on a placebo pill, and two times greater odds of quitting versus those on Zyban," said Dr. Mitchell Nides, head of the Los Angeles clinical trials.

Chantix was approved to be taken as a one-milligram pill, twice-a-day, for 12 weeks -- a period that can be doubled to increase the likelihood patients will stay off cigarettes, according to the FDA.

Chantix will be available in the second half of the year, a spokesman for Pfizer said.

Chantix is not intended to be used with other smoking-cessation aids, and is intended for people aged 18 and older. The most common side effects reported in the clinical trials were abnormal dreams and nausea. Pfizer declined to say what Chantix will cost.