Tuesday, February 13, 2007
Vaccinating Against Vices
Developing a pill or a vaccine for a specific drug addiction has long been one of the tantalizing potential rewards of addiction research. Now a company in Florida has garnered national attention, a spate of clinical trails, and a positive response from the National Institute on Drug Abuse (NIDA) with a compound called NicVAX, aimed at nicotine addiction. In addition, Celtic Pharma in Bermuda is working on a similar product for cocaine addiction.
The idea of vaccinating for addictions is not new. If you want the body to recognize a heroin molecule as a foe rather than a friend, one strategy is to attach heroin molecules to a foreign body--commonly a protein which the body ordinarily rejects--in order to switch on the body’s immune responses against the invader. The idea of a vaccine for cocaine, for example, is that the body’s immune system will crank out antibodies to the cocaine vaccination, preventing the user from getting high. A strong advantage to this approach, say NIDA researchers, is that the vaccinated compound does not enter the brain and therefore is free of neurological side effects.
Preliminary research at the University of Minnesota showed that a dose of vaccine plus booster shots markedly reduce the amount of nicotine that reaches the brain. Animal studies have shown the same effect. NicVAX, from Nabi Biopharmaceuticals, consists of nicotine molecules attached to a protein found in a species of infectious bacteria. When smokers light up, antibodies attack the protein-laden nicotine molecules, which, further encumbered by these antibodies, can no longer fit through the blood-brain barrier and allow the user to enjoy his smoke.
That, at least, is the idea. It is a difficult and expensive proposition, the closest thing to a miracle drug for addiction, but it does not specifically attack drug craving in addicted users. The idea of vaccination is that, once a drug user cannot get high on his or her drug of choice, the user will lose interest in the drug.
This assertion is somewhat speculative, in that users of the classic negative reinforcer, Antabuse, have found ways to circumvent its effects--primarily by not taking it. There remain a wealth of questions related to the effects of long-lasting antibodies. And it is sometimes possible to “swamp” the vaccine by ingesting four or five times as much cocaine or nicotine as usual.
Drugs that substantially reduce the addict’s craving may yet prove to be a more fruitful avenue of investigation. While several anti-craving medications have been approved for use by the Food and Drug Administraton (FDA), no vaccines have made it onto the approved least yet.
For more on pharmaceutical approaches to fighting drug addiction, see my website at http://www.dirkhanson.org