Novel Anti-Cocaine Vaccine
Scientists from the Weill Cornell Medical College, in New York, the United States, reveal the test results of their newest anti-cocaine vaccine. The vaccine was tested on primates and thus came one step closer to the clinical trials on humans. Their paper was published in the online journal Neuropsychopharmacology earlier this week. The team demonstrated the effectiveness of their vaccine through a radiological technique that showed that the drug was stopped from entering the brain.
Dr Ronald Crystal, the main author of the study reports that “The vaccine eats up the cocaine in the blood like a little Pac-man before it can reach the brain”, adding that he believes that the new vaccine offers a win-win strategy for cocaine abusing patients. Estimates show that there are approximately 1.5 million users in the United States alone that are trying to give up their addiction. Dr Crystal expects the vaccine to enter human clinical trials within the upcoming year.
Cocaine is a compound that is obtained from the coca plant leaves. It is a psychostimulant, an anesthetic and an appetite suppressant. Its effect is obtained through the blocking of the dopamine recycling process from two distinct areas of the brain. These areas are the putamen, found at the base of the forebrain and the caudate nucleus, located within the basal ganglia of the brain. The growth of dopamine levels at the nerve endings it provokes the cocaine high effect. The innovative vaccine developed by the research team uses a combination of a particle that imitates the cocaine structure and parts of the common cold virus.
According to Dr Crystal, the organism responds to the injection of the novel vaccine with an immune response that affects the virus itself and the cocaine-like molecule that is attached to the virus. Thus, the immune system becomes able to treat the cocaine molecule as an intruder. With their new capability, the immune cells can produce antibodies against cocaine immediately after the immune system detects its presence in the organism.
Their first study revealed that the injection of the new vaccine caused the immune system of the mouse models to create an impressive response against the virus contained within. Moreover, the mouse models that received both the vaccine and cocaine were observed to be significantly less hyperactive, in comparison to mouse models which received cocaine without the vaccine.
However, in the current study, the research team wanted to precisely determine the effectiveness of the anti-cocaine vaccine in primates. The organism of primates is considered to be much closer to that of humans, in comparison to mice. In order to solve this puzzle, researchers created a tool that measures the amount of cocaine that is attached to the dopamine transporter. This is a membrane protein that pumps dopamine from the synapse to the cytosol. When cocaine reaches the brain, it binds to the dopamine transporter, thus blocking its ability to recycle synaptic dopamine. This further leads to the drug high effect.
Researchers used an isotope tracer in order to track the dopamine transporters. Through the use of PET (Positron Emission Tomography), researchers were able to observe the activity of these transporters and measure the amount of isotope tracer that was attached to the transporter, both in the presence and absence of cocaine. The first assessment showed little to no difference between the presence of the tracer in vaccinated and non-vaccinated primates. However, when cocaine was given to the tested primates, the activity of the tracer dropped significantly in the non-vaccinated group. These results reveal that in the non-vaccinated group, cocaine displaced the isotope tracer.
Precedent studies have shown that it takes a minimum of 47% of the transporter to be occupied with cocaine before any drug high effects occur in human patients. Dr Crystal’s study shows that their novel vaccine causes the dopamine receptor to be occupied with cocaine by less than 20%. “This is a direct demonstration in a large animal, using nuclear medicine technology, that we can reduce the amount of cocaine that reaches the brain sufficiently so that it is below the threshold by which you get the high”, affirmed Dr Crystal.
The current results of the study show that the effect of the vaccine lasts for as many as 7 weeks on primates and approximately 4 months on mice. Dr Crystal concluded that if the vaccine will pass the human clinical trials, it is very probable that patients will need booster shots. However, at the current time, the amount of booster shots needed and the frequency of administration is unknown.