Nicotine vaccines.

Smoking is a global healthcare problem. Current smoking cessation rates using behavioral counseling and pharmacotherapeutic interventions have had modest success, with ∼1:5 smokers remaining abstinent long-term. Nicotine vaccines are a new class of immunotherapeutics under development. It is believed that anti-nicotine antibodies arising from vaccination capture nicotine and prevent or reduce its entry into the brain, as the antibody-bound nicotine is too large to cross the blood-brain barrier. This in turn decreases the pleasurable effects of smoking, reducing or eliminating positive reinforcement, thereby making it easier for a smoker to quit smoking. Four vaccine candidates have advanced into clinical testing with mixed success. Proof-of-concept has been established in that individuals with higher levels of anti-nicotine antibodies were observed to have higher smoking cessation and abstinence rates. Recently, the most advanced candidate vaccine, NicVAX, failed to meet the primary endpoint in two large phase III studies, although the correlation of higher abstinence rates in subjects with higher immunity to nicotine was observed. Although the field has had setbacks, the magnitude of the tobacco epidemic and the positive pre-clinical research and observed clinical trends indicate continued research is warranted. Several avenues are being actively pursued: a) improving vaccine potency by introducing novel carriers and/or adjuvants to stimulate higher immune response b) targeting subjects who have a robust response (e.g. personalized medicine) c) combining vaccines with pharmacotherapy for maintenance of abstinence/relapse prevention.