Unlike the heroin-specific vaccine we covered last year, an international team of scientists from the University of Adelaide in Australia and the University of Colorado Boulder has now found a way to block addiction to various opioid drugs, including heroin and morphine. Importantly, the new approach doesn’t negatively affect the pain-relieving properties of these drugs.
The central nervous system and the immune system both play important roles in the development of an addiction, with opioid drugs such as heroin and morphine binding to an immune receptor known as Toll-like receptor 4 (TLR4) in a similar way to the normal immune response to bacteria. Dr. Mark Hutchinson, ARC Research Fellow in the University of Adelaide’s School of Medical Sciences says, “The problem is that TLR4 then acts as an amplifier for addiction.”
In studies on rats using (+)-naloxone, a drug that automatically shuts down the opioid addiction by altering brain chemistry to stop production of the feel-good chemical dopamine, the researchers found that blocking the immune response is all that is required to prevent cravings for opioid drugs.
“Our studies have shown conclusively that we can block addiction via the immune system of the brain, without targeting the brain’s wiring,” said Hutchinson, who was lead author of the study.
“This work fundamentally changes what we understand about opioids, reward and addiction,” adds senior author Professor Linda Watkins, from the Center for Neuroscience at CU-Boulder. “We’ve suspected for some years that TLR4 may be the key to blocking opioid addiction, but now we have the proof.
“The drug that we’ve used to block addiction, (+)-naloxone, is a non-opioid mirror-image drug that was created by Dr. Kenner Rice in the 1970s,” Watkins said. “We believe this will prove extremely useful as a co-formulated drug with morphine, so that patients who require relief for severe pain will not become addicted but still receive pain relief. This has the potential to lead to major advances in patient and palliative care.”
The researchers say clinical trials may be possible within the next 18 months.