Abstract 3712: A Randomized Placebo-Controlled Trial of a Conjugate Nicotine Vaccine (NicVAX®) in Smokers Who Want to Quit: 12 Month Results
Background: Cigarette smoking triples the risk of dying from heart disease among middle-aged men and women. A nicotine vaccine (NicVAX®) has been developed to produce nicotine-specific antibodies as a means of reducing entry of nicotine into the brain as an aid to smoking cessation.
Objective: To assess 12-month safety, efficacy and immunogenicity of NicVAX in smokers who want to quit.
Method: Randomized, double-blinded, placebo-controlled multicenter clinical trial with 2 dose levels of NicVAX (200μg & 400μg) and 2 schedules. Generally healthy adults who smoked ≥ 15 cigarettes/day were recruited. Subjects were randomized 2:1, active:placebo, at 9 sites in the US. The primary endpoint was self reported continuous abstinence for weeks 19 – 26 confirmed by expired CO levels of ≤ 8 ppm. Secondary endpoints include point prevalence abstinence at 12 months.
Results: 301 subjects (52% female) with a mean age of 48, smoking on average 24 cigarettes/day were enrolled. A pre-defined analysis of antibody levels for subjects receiving NicVAX were reviewed and divided into low and high responder groups, with the top 30th percentile representing the high responder group. Analysis for the primary endpoint demonstrated that 15/61 (24.6%) of subjects having the highest antibody titers achieved an 8 week period of continuous abstinence between weeks 19 –26, compared to 13/100 (13.0%) for the subjects who received placebo (p=0.04). In contrast, the quit rate for those subjects that did not achieve a high antibody titer was not significantly different from placebo (14/140, 10%). There was a significant relationship between anti-nicotine antibody levels and continuous abstinence from smoking (p=0.0001). NicVAX was well-tolerated and showed no differences in adverse events or in local/systemic reactions between placebo and each active vaccine group.
Conclusion: Proof-of-concept has been established by the strong correlation of high antibody titers with smoking abstinence. Interim data (6 months post vaccination) demonstrate that generating antibodies to nicotine may be a useful approach for aiding smoking cessation. This study will be completed in Sept 2007. Immunogenicity, sustained smoking cessation and relapse rates at 12 months after vaccination will be presented.