Thursday, November 8, 2007
Nicotine Vaccine Doubles Quit Rate in Human Trials
NicVax still showing promise against cigarette addiction
Nabi Biopharmaceutical announced this week that an experimental vaccine it has been testing against nicotine addiction had shown itself to be effective in human trials. Volunteers were more than twice as likely to quit, compared to a control group whose members were injected with a placebo.
The company-funded study gave volunteers five injections of NicVax, Nabi’s proprietary drug, or else a placebo. In regulatory filings, the company claims that the vaccine triggers an antibody response, which prevents nicotine molecules from reaching the brain. The antibodies bind with the nicotine molecules, making nicotine too large to cross the exceedingly fine blood-brain barrier of the brain. Roughly 15 per cent of smokers who received injections of NicVax were nicotine-free after one year. For comparison, early studies of Chantix as an anti-smoking medication show a quit response rate in the range of 20 per cent for heavy smokers. Studies of NicVax undertaken last year were also positive. It is one of several nicotine vaccines currently under development, and while it is farthest along in the FDA pipeline, it is still a year or two away from any possible commercial introduction.
Vaccines for specific addictive drugs represent one of two different approaches to developing pharmaceuticals for addiction treatment. The other approach, represented by Chantix and Zyban, decreases drug craving by altering the neuroregulation of dopamine and other substances in the brain. In this respect, these two drugs, which are non-addictive, are related to nicotine gums and patches, which also attempt to diminish cravings for cigarettes.
A vaccine like NicVax, however, does not attack the craving for nicotine. It contains no nicotine and is non-addictive. Rather, the vaccine makes the attempt to assuage nicotine cravings an impossible task. And in this respect, NicVax resembles Antabuse for alcoholism--except that the vaccine does not cause the smoker to become seriously ill when he or she takes a puff. . (The company reported that side effects were “well tolerated.”) It simply (or not so simply) cancels out the nicotine high altogether, or at least that is the idea. It is unclear to what extent the antibody reaction prevents nicotine binding in other areas of the body where nicotine-type receptors are found, such as acetylcholine receptors in muscle tissue.
In addition, NicVax must be injected, while Chantix and Zyban or taken orally. “Some people prefer a shot and some people will do anything to avoid one,” Rennard said. “It’s important to have options.”
Stephen Rennard of the University of Nebraska Medical Center, one of the authors of the company’s study, which is funded by a grant from the National Institute on Drug Abuse (NIDA) and is now in midstage, said that when smokers “don’t get the hit they would normally get, it makes it easier for them to quit because smoking doesn’t really do it for them any more.”
The results were presented at the American Heart Association Scientific Sessions in Orlando, Florida. “This double-blind, placebo-controlled trial has demonstrated [that] there is a correlation between antibody level and the ability of patients to quit smoking and remain abstinent over long periods of time,” Rennard told the group. Leslie Hudson, CEO and Interim President of the company, said he was “excited and encouraged.” Nabi Biopharmaceutical, headquartered in Boca Raton, Florida, is traded on the NASDAQ stock market [NABI].