Evidence-Based Reviews

Vaccine for cocaine addiction: A promising new immunotherapy

Current Psychiatry. 2010 September;9(9):16-A

References

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DR. SOMOZA: In phase 1 and phase 2 studies, there haven’t been any problems at all.⁶ Theoretically, we could see some reaction at the injection site such as bruising or red or inflamed skin. In some cases with protein vaccines they’ve seen systemic reactions like fever. There’s also a risk of serum sickness, but this is theoretical based on other protein-based vaccines.⁷

DR. ANTHENELLI: Are there any data that address the safety of long-term TA-CD use?

DR. SOMOZA: We do not have any data on long-term use, but we know what happens over several months. When this project began 12 years ago, investigators worried that if the vaccine prevents cocaine from getting to the brain, cocaine-dependent individuals would just take more and more of the drug and suffer serious consequences. However, in preliminary studies, people have taken as much as 10 times their “normal” amount of cocaine with no adverse events. It looks like the vaccine may ameliorate some of cocaine’s effects on the heart. We’re certainly not encouraging study subjects to try to override the vaccine blockade, but these preliminary data at least minimize some of those concerns.

DR. ANTHENELLI: In clinical trials of TA-CD, during the 8-week ramp-up period where you’re waiting for patients’ antibody titers to get high enough to have a therapeutic effect, do trial participants receive other treatment?

DR. SOMOZA: Participants receive state-of-the-art cognitive-behavioral therapy (CBT) once a week. We do this to help patients look for triggers to cocaine use and how to handle them, but also to encourage them to stay in the study. It’s important that people who enroll in our trials are motivated to stop using. Many patients who have been using cocaine for years haven’t been able to own a house, get married, or even buy a car because all of their money is spent on cocaine. Eventually they decide it’s not a good idea to keep using forever. These are the participants we’d like to find.

There are other ways of increasing retention, such as rewarding patients for coming to appointments, providing urine for toxicology screens, or getting the boosters. We’re hoping contingency management will help keep patients in the trial.

How TA-CD will aid treatment

Clinical Point

In addition to CBT, vaccinated patients also could receive other pharmacologic treatments

DR. ANTHENELLI: How do you envision TA-CD could be used in clinical practice?

DR. SOMOZA: It could become another tool in our armamentarium for treating cocaine dependence. Currently, there are no FDA-approved medications for cocaine dependence, although some pharmacologic treatments are being studied (Table).^8-13 When a patient comes in to be vaccinated, he or she also could receive other treatments if they are available, and the effect potentially would be additive. We would also use CBT because cocaine dependence is a very complex disorder. In CBT patients identify triggers that cause them to want to use and learn how to combat them and make better decisions.

DR. ANTHENELLI: Some research shows that TA-CD doesn’t stop cocaine use altogether but reduces use. Will that be a deterrent for clinicians who wish to help patients achieve absteinence?

DR. SOMOZA: That’s true about any medication we develop for addictions. I think it is magical thinking to say that you can give patients a pill and they will be abstinent for the rest of their lives. If you look at tobacco or alcohol, in practice abstinence is an end point that one has to approximate successively. In addition, permanent abstinence from cocaine is virtually impossible to measure. Because the half-life of benzoylecgonine (BE), the principle metabolite of cocaine, is 6 to 8 hours, this limits the effectiveness of urine toxicology screens in monitoring abstinence. Cocaine-dependent patients might not have used the drug the day before a urine toxicology screen. If a patient says he is abstaining from cocaine, it would be difficult to document it quantitatively without obtaining urine BE levels every day or every other day.

I think clinicians need to get used to the fact that we have to treat cocaine dependence in an incremental manner. A pharmacotherapy that would reduce use and hopefully limit the problems people are having as a result of cocaine use would be a positive step.

DR. ANTHENELLI: If TA-CD is found to be effective, what is the earliest it might come into clinical use?

Clinical Point

TA-CD may be available to clinicians in 7 to 10 years if it is found to be effective

DR. SOMOZA: I would speculate that it would be 7 to 10 years.