U-47700 is an opioid analgesic drug developed by a team at Upjohn in the 1970s that acts as a selective agonist of the -opioid receptor with a Kd value of 5.3 nM compared to 910 nM for the -opioid receptor and has around 7.5 x the potency of morphine in animal models.
U-47700 is a structural isomer of the earlier opioid AH-7921 and the result of a great deal of work elucidating the quantitative structureactivity relationship of the scaffold.
Upjohn looked for the key moieties which gave the greatest activity and posted over a dozen patents on related compounds, each optimizing one moiety until they discovered that U-47700 was the most active.
U-47700 became the lead compound of selective kappa-opioid receptor ligands such as U-50488, U-51754 (containing a single methylene spacer difference) and U-69,593, which share very similar structures.
Although not used medically, the selective kappa ligands are used in research.