More and more, vaccine strategists are targeting drugs of abuse, like cocaine, heroin and nicotine. The science behind the vaccines is to generate antibodies that bind with the drug of abuse in the bloodstream and prevent it from reaching the brain to begin psychoactivity. Many of these vaccines are already in pre-clinical testing, while others are still being dreamed up. Scientists may be touting this as a major advance for public health and safety, but these vaccines may not fix all the problems and appear to have several drawbacks that warrant concern.
The Strongest Contenders
Researchers from Weill Cornell Medical College developed a vaccine that combines a drug similar to the structure of cocaine with an inactivated common cold virus. The investigators expect that as the body responds to the cold virus with an immune response, it will also see the cocaine impersonator as an enemy and sequester it in the bloodstream. This trained response will prompt the body to attack the next time cocaine enters the body.
In preclinical testing, the researchers used primates and found that the vaccine reduced the amount of cocaine that reached the central nervous system and brain, thus preventing a mind-altering high from the cocaine. The beneficial effects of the vaccine lasted only seven weeks in the primates, so the researchers expect humans will need booster shots.1 2
In efforts to tackle heroin addictions, researchers from The Scripps Research Institute struggled with designing a vaccine because heroin metabolizes so quickly in the bloodstream after injection. Their experimental vaccine creates antibodies to attack heroin and its psychoactive products and prevent heroin from reaching the brain.
In a preclinical study, the team found that heroin-dependent rats exhibited fewer signs of addiction (i.e., heroin reward, drug seeking behavior) and no sign of relapse when given the vaccine. The vaccine does not target opioid receptors, such as methadone or buprenorphine, so it could be used alongside these treatment options.3 The next step for the heroin vaccine according to the Scripps investigative team: find a pharmaceutical company partner to sponsor the human clinical trials.4
Scripps researchers have also been working on a methamphetamine vaccine. Their challenge with the methamphetamine molecule was that it has a simple structure and can go unnoticed by the immune system and it lingers in the nervous system. As a response, the investigators linked the main active ingredient to a larger, antibody-provoking carrier molecule. Testing in rats found that the vaccine kept more of the methamphetamine in the bloodstream, rather than in the nervous system, and the rats exhibited fewer signs typical of meth intoxication. However, the vaccine was given in four doses over 12 weeks, showing the need for multiple injections to induce any effect.5 6
Nicotine vaccines may have reached the human clinical testing level, but they have not amounted to much success. In one 2013 study, researchers tested the vaccine in 11 individuals who smoked 19 cigarettes per day and had a smoking history of 10 years, on average. The vaccine reduced the amount of nicotine that binds to nicotinic acetylcholine receptors and the participants reduced their urge to smoke, as well as their overall cigarette use by 40%, but not their craving for nicotine. This study focused only on the period immediately following immunization, and it is unknown if these reduced cigarette cravings can actually sustain decreased nicotine intake.7 8
Questions Behind the New Vaccines
The first issue is that addicts have a stereotype, which includes a lack of money and a lack of motivation to quit. Many addicts are welfare recipients, so the question of who pays remains. An addict could take the cocaine vaccine, then use cocaine and not feel the regular and expected high. They may be tempted to use more cocaine to try to compensate for the diminished effects and potentially overdose.9 These vaccines also would require a true dedication, especially given the expectation from early research that multiple doses and vaccine boosters will be necessary to have a long-lasting effect. Dedication and patience are not virtues associated with the addict group. The person could also seek other drugs that produce the same effects, but are structurally different with no effect from the vaccine.
Besides multiple doses and booster requirements, another issue revealed in the ongoing research projects is the need for high concentrations of antibodies to induce the effect, as well as the fact there is individual variability in antibody formation.10
An ethical issue is how these vaccines would be used. Would doctors or policymakers see a reason to use them as preventive measures in at-risk populations, such as teenagers or pregnant addicts in an attempt to protect the unborn from developmental birth defects?11
With too many unanswered questions, more thorough research is necessary before bringing any of these candidates to market.
1 Maoz A, Hicks MJ, Vallabhjosula S, et al. Adenovirus Capsid-Based Anti-Cocaine Vaccine Prevents Cocaine from Binding to the Nonhuman Primate CNS Dopamine Transporter. Neuropsychopharmacology. 2013.
2 Cornell University. Cocaine Vaccine Passes Key Testing Hurdle. Press Release. May 10, 2013.
3 Schlosburg JE, Vendruscolo LF, Bremer PT, et al. Dynamic vaccine blocks relapse to compulsive intake of heroin. Proceedings of the National Academy of Sciences. 2013.
4 The Scripps Research Institute. Preclinical Study Shows Heroin Vaccine Blocks Relapse. Press Release. May 6, 2013.
5 Miller ML, Moreno AY, Aarde SM, et al. A Methamphetamine Vaccine Attenuates Methamphetamine-Induced Disruptions in Thermoregulation and Activity in Rats. Biological Psychiatry. 2013;73:721-8.
6 The Scripps Research Institute. Meth Vaccine Show Promising Results in Early Tests. Press Release. Nov. 1, 2012.
7 Esterlis I, Hannestad JO, Perkins E, et al. Effect of a Nicotine Vaccine on Nicotine Binging to B2*-Nicotinic Acetylcholine Receptors In Vivo in Human Tobacco Smokers. American Journal of Psychiatry 2013;170:399-407.
8 Glatter R. Nicotine Vaccine May Help You Quit Smoking. Forbes. Feb. 26, 2013.
9 Rodriguez JM. New Vaccine Takes the Fun Out of Cocaine. Care2. Sept. 10, 2013.
10 Kantak KM. Vaccines Against Drugs of Abuse. Drugs. 2003;63:341-52.
11 See Footnote #9.