New Vaccine Against Methamphetamine Drug Addiction Shows Promising Results
A research team from TSRI (The Scripps Research Institute) have successfully conducted rat tests with a new methamphetamine vaccine. The laboratory rats that were injected with the new vaccine showed a high level of protection against methamphetamine intoxication. According to the research team, if further tests reveal that the vaccine has the same effect on human subjects, it could lead to novel treatment for methamphetamine addiction. Methamphetamine addiction is estimated to affect approximately 25 million people on the globe.
According to associate professor and lead author of the study, Michael Taffe, the result of this study indicates the possibility of consequent clinical trials. Taffe is an associate professor in the Committee on the Neurobiology of Addictive Disorders.
Throughout the last 20 years, methamphetamine became one of the most abused drugs in the world, along with Marijuana, Cocaine and Hallucinogens. According to various studies, more than 400 thousand users are suspected in the United States. Furthermore, in several states, methamphetamine is accounted for the most treatment admissions, compared to other drugs. One of the reasons that holds methamphetamine from being approved for treatment is its increased addictiveness.
In the past few years, several research teams have studied different vaccines against these addictive drugs. These specific vaccines work the same way as traditional antiviral and antibacterial vaccines, however, instead of targeting bacteria and viruses, they target drug molecules. The antibody response caused by the vaccines would stop the drug molecule from reaching its target, the brain, thus inhibiting the impulse to further take the respective drug.
Both anti-nicotine and anti-cocaine vaccines are already undergoing clinical trials. Precedent anti-methamphetamine vaccines have shown discouraging results. Due to its simple molecular structure, the immune system doesn’t easily recognize the methamphetamine molecule. Methamphetamine and amphetamine, which is the main metabolite, tend to loiter in the central nervous system, thus allowing even a small amount of drug molecules to have a major impact. “The simple structure and long half-life of this drug make it a particularly difficult vaccine target”, said chemistry professor Kim Janda from the Skaggs Institute for Chemical Biology at TSRI.
A couple of years ago, a research team led by professor Janda created six new anti-methamphetamine vaccines. Each of the vaccines contained an active ingredient which was a molecule derived from the methamphetamine molecule. This molecule was linked to a carrier molecule. The link between the two molecules was needed because the derived molecule could not provoke an immune response by itself. According to the results of early tests conducted on laboratory mice, 3 of the 6 vaccines managed to provoke an immune response towards methamphetamine. Later studies conducted by professor Taffe showed that one particular vaccine, MH6, was able to block two specific effects of methamphetamine – the loss of the ability to regulate body temperature and the increase in physical activity.
In this current study, researchers investigated the effects of the MH6 vaccine more thoroughly. Through the use of a different technique, researchers reconfirmed that the vaccine can prevent both the hyperactivity and the rise in temperature associated with methamphetamine exposure. Crucial for these beneficial effects is a strong antibody response. In comparison with a control group, researchers observed that a larger quantity of the drug was held in the bloodstream when the rats were vaccinated. “These are encouraging results that we’d like to follow-up with further animal tests, and, we hope, with clinical tests in humans some day”, said research associate Michelle Miller.
A different research group reports that studies for antibody-based addiction treatment also show promising results. For this treatment approach, anti-methamphetamine antibodies are grown through standard biotechnology methods. These antibodies are further injected into the animal in a highly concentrated dose. Antibody treatment approaches are used to treat chronic conditions of the immune system and different types of cancer. However, these particular methods are very expensive, thus making in an improbable treatment scheme because methamphetamine addicts usually have no health insurance and their treatment schemes are funded by the government.
In theory, this new active vaccine would be cheap to make and more efficient than the antibody therapy because of its longer period of protection. However, in practice, the vaccines that are being investigated last shorter than expected.
“Extending the duration of protection is the next big scientific challenge in this field”, concluded professor Taffe.
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