Offering tobacco users a vaccination to help ease, or potentially cure, their nicotine addiction is showing promise in clinical trials.
Researchers at Wake Forest University Baptist Medical Center want to advance the treatment by figuring out why some cigarette smokers are more addicted to nicotine than others. The National Institutes of Health has provided a $2.5 million grant for the study.
"We want to understand the difference between the person who becomes addicted and the person who can be a casual smoker," said Pradeep Garg, the lead researcher for the Wake Forest Baptist effort, which also involves Duke University Medical Center. Garg is a professor of radiology and director of the center's Positron Emission Tomography (PET) Center.
Their research, published recently by Proceedings of the National Academy of Sciences, studies how long it takes nicotine to reach peak levels in the brains of cigarette smokers. The strategy involves using PET imaging to observe nicotine distribution in organs as participants smoke.
"The bottom line is that if we can effectively block nicotine entry in the brain, we will have effective therapy," Garg said.
"Having an accurate understanding of the mechanism of anti-nicotine immunotherapy will help us improve its treatment efficacy. It could lead to better patient management and may help develop better vaccines in the future."
The most advanced effort involving nicotine vaccination is being done by Nabi Biopharmaceuticals. It is in a Phase III clinical trial with NicVax, which aims to prove a drug's effectiveness on humans.
Nabi has reached a drug-development partnership with GlaxoSmithKline regarding NicVax. Garg said his group is working with a different vaccine that he declined to identify.
According to an article in The Washington Post, the goal of NicVax is to cause the immune system to create antibodies that bond with the nicotine molecule if it enters the bloodstream.
The result is a molecule too large to pass along to the brain, thus lowering the pleasure the smoker receives from nicotine and the desire to smoke.
That Nabi officials are touting a 16 percent quit rate among participants shows that a vaccination "will not be a cure-all for nicotine addiction," said David Burns, an emeritus professor of the medical school at the University of California at San Diego.
By comparison, other smoking-cessation products typically have between 10 percent and 20 percent success rates. The rate is determined in part by the length of time since the person stopped smoking or used tobacco products.
"It is an interesting and promising approach as another smoking-cessation tool," Burns said.
Garg said that figuring out how long the vaccine remains effective could determine how often it is given and whether it would require booster shots.
"No vaccine will serve as a turn-off switch, but will take several weeks to reach efficiency and may require the use of other cessation products," Garg said.
A potential challenge with NicVax is that other prescription medications approved to help smokers over age 18 quit, particularly Zyban and Chantix, have had significant side effects. In 2009, the Food and Drug Administration ordered that those drugs carry "black box" warnings of the risk of depression and suicidal thoughts.
The American Cancer Society said that of the 44 million Americans who smoke, about 70 percent said they want to quit and 40 percent are successful with initial efforts.
But only up to 7 percent actually quit for good without help.
Garg and Burns said that not enough research has been done to determine whether the vaccine could play a preventive role in keeping someone from becoming addicted, or how well it could work on smokeless-tobacco products.
"The vaccine is more geared now toward breaking addiction than preventive, but that potential can be investigated," Burns said. "The level of how quickly someone becomes addicted to nicotine and whether there is a generic susceptibility to nicotine addiction is being researched.
"There tends to be more important determinants leading to addiction," Burns said, citing peer pressure, cigarette marketing and family members smoking.
Garg said it is possible that the research "takes us to a place where the vaccine can help people as they approach the addiction stage."
rcraver@wsjournal.com
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