Researchers say addiction-free opioids possible

A team of US researchers from Wake Forest University has tested an opioid that appears to stop pain in non-human primates without causing addiction. The results were published in Science Translational Medicine. While clinical trials on humans are still years away, the transferability of the results of opioid tests from non-human primates to humans has been quite good in past studies, raising hopes that the experimental drug will eventually be a factor in winning the battle against opioid addiction.

The experimental drug, AT-121, affects the human body in a different manner than traditional opioids. To relieve pain, traditional opioids activate an opioid receptor called the mu receptor. But, the human body has three other opioid receptors called delta, kappa, and nociception opioid peptide (NOP). All four receptors block pain in different ways but activating the mu receptor results in the addictive, euphoric high that people experience when using traditional opioids. As they continue to use opioids that activate the receptor, people’s bodies become more dependent on opioids, resulting in addiction. Once addicted, people suffer a painful withdrawal process when they stop using them.

Activating the other three opioid receptors does not result in an addiction cycle. The research team hypothesised that an opioid, such as AT-121, which activates one of the other receptors at the same time as the mu receptor, would block pain without causing addiction.

The study team conducted mild pain tests using rhesus monkeys and found that AT-121 was 100 times more potent than morphine in blocking pain. Also, the experimental drug did not appear to create a high or result in addiction. The team also noted that even high doses of AT-121 didn’t cause classic overdose symptoms. The researchers will next test AT-121 for potential long-term risks.