The worldwide opioid crisis has occasioned efforts to develop new opioids for both existing uses (pain control) as well as new indications (itch, addiction). We have focused on the discovery of compounds able to selectively activate one of the two main intracellular pathways associated with the kappa opioid receptor. This type of activity, called “functional selectivity” or “ligand bias”, has the potential to segregate many of the ultimate biological effects of therapeutic opioids.

The design and engineering of protein catalysts that carry out rare or non-natural chemistry remains a challenging contemporary goal. However, enzymes are inherently limited by their chemical composition, i.e. the reagent pool that exists in nature and the amino acids and cofactors that form their physical and catalytic core. Because of this limitation, the majority of chemical transformations developed by synthetic chemists remain, at least to our knowledge, biologically inaccessible.