To combat cigarette smoking, researchers are seeking ways to combat the habit which affects more than 45 million Americans.
One new option is a vaccine that targets the nicotine rather than the brain's reaction to it. Researchers from the University of Minnesota, supported by the National Institute of Drug Abuse and Nabi Biopharmaceuticals, have tested this new vaccine in humans with positive tolerability and efficacy.
" We are encouraged by the results of this study, which suggest that a nicotine vaccine may be a safe and potentially effective way to reduce tobacco dependence or as a relapse prevention aid," said Dorothy Hatsukami, of the University of Minnesota and lead author of the study.
The nicotine vaccine in question stimulates the immune system to develop antibodies that specifically attach to the nicotine molecules. The resulting antibody-nicotine combination is too large to pass through the blood to the brain, resulting in less nicotine in the brain.
Animal studies have confirmed that the vaccine works by reducing and also slowing the amount of nicotine that enters the brain, reducing nicotine's addictive effect.
Preliminary human studies have been conducted to determine the safety of the nicotine vaccine, as well as the best dosage and optimal dosing schedules.
A multi-site clinical trial randomly assigned 68 smokers to receive different doses of vaccine, or placebo, and followed them over 38 weeks. The vaccine was well tolerated among the subjects. Aches and tenderness at injection sites were reported; systemic reactions included headaches, malaise or myalgia or muscle pain, although these latter reactions were similar between the vaccine and placebo.
Most symptoms were mild and self-limited, resolving within a few days, and none required medical intervention.
There was no evidence of withdrawal after vaccine injection or evidence that smokers increased smoking intensity to compensate for the reduced nicotine in the brain.
Preliminary analysis shows that the highest dose of vaccine in participant smokers, who had not necessarily been interested in quitting, showed significantly higher rates of 30-day abstinence than placebo.
" Two additional human clinical trials with other nicotine vaccines have been conducted which showed similar safety profiles and higher abstinence rates in the highest nicotine vaccine dose or antibody level groups, and we hope to conduct further trials to confirm these results," said Hatsukami.
Source: American Association for Cancer Research, 2005