Researchers presenting at the American Association for Cancer Research meeting in Baltimore on Wednesday reported strong safety and efficacy results for NicVAX.
"We saw a significant effect," said lead author Dorothy K. Hatsukami, the Forster Family Professor in Cancer Prevention at the University of Minnesota's School of Medicine, in Minneapolis.
The effects were significant enough to merit moving on to a full-blown clinical trial, she added.
"It's absolutely worth it," Hatsukami stated. "There's a lot of promise for this vaccine, not just because of our study, but also because of other studies."
NicVAX is now the frontrunner in the field, most likely to be the first to get results to the U.S. Food and Drug Administration for possible approval.
"They're getting close to phase 3, which is the final step before presenting to the FDA," said Thomas J. Glynn, director of Cancer Science and Trends at the American Cancer Society. "We're still talking a couple of years, but they are pretty far ahead of the other two. It's a serious effort. It's no fly-by-night."
The other two nicotine vaccines under development may be as much as four to six years away from market, Glynn added.
The market for such a vaccine is huge, with about 50 million people in the United States still smoking. The habit contributes to a host of diseases and is the number one preventable risk factor for cancer. Lung cancer is the leading cause of cancer-related deaths, causing more deaths than the other five top cancers combined.
"This vaccine opens up a world of possibilities," Glynn said.
At least two other vaccines are in development. In addition, Varenicline and Rimonabant, which are not vaccines, have reported about 50 percent quit rates at 12 weeks, and may be approved by the FDA within a year.
The basic principles across the different vaccines are similar: The vaccine stimulates the body's immune system to produce antibodies that then attach to the nicotine molecule. In animal studies, this has been shown to slow delivery of nicotine to the brain while also decreasing the amount reaching the brain. The reason? The nicotine/antibody compound is too big to cross the blood-brain barrier.
"It's such a novel way of treating an addiction because it's not targeting any part of the brain," Hatsukami said. "It's targeting the molecule itself."
The current study, supported by the National Institute of Drug Abuse and Nabi Biopharmaceuticals, was designed to look at safety, as well as levels of antibodies produced.
Sixty-eight smokers were randomly assigned to receive different doses of the vaccine or a placebo. The participants were not recruited because they had expressed an interest in quitting.
Although the study was not specifically designed to look at cessation, quit rates were impressive: 38 percent of the participants quit smoking for 30 days.
"That's pretty good for people coming in for non-treatment," Hatsukami said. "We didn't even provide counseling unless they asked for it."
Higher vaccine doses elicited better antibody responses. Participants receiving the highest dose were more likely to abstain from cigarettes for 30 days.
"Far more people quit in the highest dose," Hatsukami said. "It looks like vaccines do have promise in terms of helping people quit smoking."
Some participants reported aches and tenderness at the injection site, while some also reported headaches, malaise and muscle pain. Most of these side effects went away within a few days, the researchers said.
There were no differences in withdrawal symptoms between those receiving the vaccine and those receiving a placebo.
There also appeared to be no "compensatory smoking behavior," meaning vaccine recipients did not puff harder or smoke more cigarettes to compensate for the effect.
Several questions still remain, Glynn pointed out: How long will the vaccine be effective? Will smokers need a booster? Will it be a relapse preventer? And is this something that could be given to a 9-year-old to prevent him or her from taking up the habit, much like the measles vaccine prevents measles?
"The big question is, is this one of the magic bullets? My heart says yes and my head says no," Glynn said. "[But] it will enable us to start tailoring treatment even more for cessation."
More information
To learn more about nicotine addiction, visit the National Institute on Drug Abuse.
