Is AT121 the perfect opioid?

Abstract

Opioids are the most powerful and effective analgesics available today. Their dark side is reflected in the growing number of patients addicted to their use around the world, mainly in the United States. Since the discovery of the first synthetic opioids, the pharmaceutical industry has been searching for an analgesic that does not generate tolerance or dependence, nor adverse respiratory effects.

Most opioids are mu receptor agonists, whose activation increases the synaptic availability of dopamine, a neurotransmitter that is a carrier in reward circuits. However, a fourth opioid receptor has recently been described: the nociceptin/orphanine receptor. Its activation inhibits the release of dopamine, preventing the positive reinforcement that occurs after drug consumption. AT-121 is a bifunctional MOP/NOP agonist that has been tested in non-human primates with promising results in terms of analgesic potency, fewer systemic side effects, and lower rate of addiction and abuse. Such characteristics make this molecule a hopeful weapon in the treatment of chronic pain or addiction to opioid drugs. In recent years, different bifunctional agonists have been explored in rodents and non-human primates with interesting results; we are therefore awaiting future research in humans.