Designer opioids to target pain

Morphine and other alkaloids from the opium poppy are μ-opioid receptor agonists that have been used to treat pain for many centuries. These authors used a computational approach to dock over three million small molecules to the μ-opioid receptor. Structure-based optimization of the most promising structures led to the identification of a potent agonist, PZM21, with exceptional subtype selectivity for the μ-opioid receptor. In mice, PZM21 generates substantial analgesia, which is fully ablated in μ-opioid receptor knockout animals. This small molecule seems to reduce the affective component of pain, without detectably altering reflexive behaviours, and has little effect on respiration.