Critical Assessment of G Protein-Biased Agonism at the μ-Opioid Receptor
G protein-biased agonists of the μ-opioid receptor (MOPr) have been proposed as an improved class of opioid analgesics. Recent studies have been unable to reproduce the original experiments in the β-arrestin2-knockout mouse that led to this proposal, and alternative genetic models do not support...
www.cell.com
Yeah you are totally right on that @Neithman. This review kind of covers why and stuff.
Basically the assays they used in cells failed to account for partial agonism so partial agonists looked like g protein biased ligands.
And they did some mechanistic stuff showing you could block respiratory depression by interfering with g protein signaling.
Finally the showed their beta arrestin knockout mouse wasn't actually a full knockout.
