The finding, published in the journal Biological Psychiatry, came from a team at The Scripps Research Institute (TSRI) after giving meth to animals that were vaccinated with the drug and not seeing any typical signs of meth intoxication in them.
Meth (methamphetamine) is a highly addictive drug, affecting approximately 25 million people globally. If this vaccine is tested and proven successful in humans too, it will give people with meth addiction a hopeful future.
"This is an early-stage study, but its results are comparable to those for other drug vaccines that have then gone to clinical trials," explained Michael A. Taffe, an associate professor in TSRI's addiction science group, known as the Committee on the Neurobiology of Addictive Disorders.
A Harmful and Commonly Abused DrugMeth has become one of the most commonly abused drugs worldwide over the past 20 years. Over 400,000 people in the U.S. are currently using meth, and in some states, such as California, meth makes up the most primary drug abuse treatment admissions.
There are currently no treatments for meth addiction. One reason is that the drug has certain qualities that make it more addictive than any other type.
Experts at TSRI and other institutions have recently been trying to develop new approaches - creating vaccines against addictive drugs. Similar to the way conventional vaccines evoke antibody reactions against bacteria or viruses, these new vaccines evoke antibody responses against drug molecules.
In order to stop the drug from creating a high in the user, and take away the motivation for using, anti-drug antibodies stop the drug molecules from getting into the brain.
Clinical trials are already in progress for vaccines against cocaine and nicotine. Although animal tests have been conducted on meth vaccines, the results were not promising.
The structure of the methamphetamine molecule is rather simple, which causes it to become fairly unnoticeable to the immune system. Since meth and its main metabolite, ordinary amphetamine, usually 'linger' when they enter the nervous system, a little dose of the drug is still likely to have a big effect.
"The simple structure and long half-life of this drug make it a particularly difficult vaccine target," said Kim Janda, the Ely R. Callaway, Jr. Professor of Chemistry and member of the Skaggs Institute for Chemical Biology at TSRI.
Promising ResultsSix potential meth vaccines were developed two years ago by Janda and colleagues. The leading active component of each was a chemical cognate of the methamphetamine molecule linked to a greater, antibody-provoking carrier molecule.
After conducting trials in mice, results showed that three of these candidates could evoke a powerful antibody reaction to meth. These 3 vaccines were then tested in rats, which allowed the team to discover the one, designated MH6, which worked best at preventing the two typical effects of meth:
- an increase in physical activity
- a loss of the normal ability to regulate body temperature
The results also showed that the vaccinated rates kept more of the drug in the bloodstream and out of the nervous system than the control rats, indicating a strong antibody response.
"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 L. Miller, leading author of the study.
"I think that this vaccine has all the right features to allow it to move forward in development," added Janda. "It certainly works better than the other active vaccines for meth that have been reported so far."
The Next Big Step - Increasing the Length of ProtectionA different team of scientists reported promising results from a separate animal test for an antibody-based treatment. Through this method, the meth high is stopped by growing anti-meth antibodies in cultured cells using standard biotechnology methods and then injected into the animal in a concentrated dose.
Cancer and chronic immunological conditions are normally treated through antibody-based therapies. However, they are usually pretty expensive and the effects of one dose do not last for more than a few weeks.
Since addicts typically do not have much money and no health insurance, a meth treatment would need to be fairly cheap. An active vaccine would not only be cost-effective, it would also protect people for months per dose, instead of weeks with traditional monoclonal antibody therapy.
However, active meth vaccine candidates do not last that long, as seen with the MH6 candidate which was given in 4 doses over 12 weeks. The authors believe an active meth vaccine would be able to bear an anti-meth antibody reaction for a longer amount of time after more modifications.
"Extending the duration of protection is the next big scientific challenge in this field," concluded Taffe.
Written by Sarah Glynn