Anti-opioid vaccine could offer bridge to overcoming addiction

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A vaccine could be a valuable addition to therapies used to combat opioid addiction, military researchers believe.

Scientists at the military’s Walter Reed Army Institute of Research announced today that they’ve developed a heroin vaccine that can block the euphoric effects of opioids in the brain—and do so without interfering with other therapies used to treat addiction. If the concept proves useful in people, it could provide a bridge to recovery for the growing population of patients trying to overcome their addiction.

The vaccine, co-developed by the National Institutes of Health (NIH) National Institute on Drug Abuse, works by producing antibodies that prevent heroin from crossing the blood-brain barrier. In a study, the researchers showed the vaccine also produces antibodies against hydrocodone, oxycodone, codeine and other commonly abused substances. The research was published in the Journal of Medicinal Chemistry.

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One of the challenges of developing anti-opioid treatments is making sure they don’t interfere with treatments that are already being used against addiction, such as methadone, buprenorphine and naltrexone. The Walter Reed scientists found no such cross-reaction between their vaccine and those compounds, nor did they find any interference with naloxone, the drug used to reverse opioid overdoses.

The researchers envisioned another potential problem with their vaccine, however: What would happen if a vaccinated addict in recovery needed pain relief due to an injury? So they tested the antibodies produced by their vaccine and discovered that they did not bind to certain other narcotics, like tramadol, nor did they bind to non-narcotic pain relievers such as acetaminophen.

"Although we are still in the early phase, this study suggests that vaccination can be used together with standard therapies to prevent the withdrawal and craving symptoms associated with opioid withdrawal," said Gary Matyas, chief of adjuvants and formulations for the U.S. Military Research Program, in a statement.

More than 90 Americans die daily from opioid abuse, according to the Centers for Disease Control. Efforts to combat the crisis range from developing alternative pain relievers to searching for new ways to reverse addiction. Among the new approaches to pain relief described in recent months is a compound that tamps down pain signals by boosting the production of the brain chemicals anandamide and 2-arachidonoylglycerol, and “mu opioid agonists” that are designed to relieve pain without causing addictive tendencies.

Many research efforts are focused on blocking the euphoric effects of opioids on the brain. In September, the Sanford Burnham Prebys Medical Discovery Institute won a grant from the NIH to develop a drug that targets metabotropic glutamate receptor 2 (mGlu2), which they believe might eliminate the influence of opioids on environmental cues that drive addiction, such as positive memories.

Preventing opioids from getting into the brain altogether is the aim of the new vaccine being developed at Walter Reed. Adherence to anti-abuse treatments—and the effectiveness of those approaches—can vary wildly among patients, the researchers point out. Therefore the vaccine could prove valuable as part of a collection of treatments, they say.