WAY-214156 is a synthetic nonsteroidal estrogen that acts as a highly selective agonist of the ERò. It is 100-fold selective for the ERò over the ERñ with an IC<sub>50</sub> of 4.2 nM (compare to estradiol with IC<sub>50</sub> values of ~3âÂÂ4 nM for both the ERñ and ERò). The drug is less selective for the ERò than is prinaberel (ERB-041, WAY-202041), another selective ERò agonist, but is more potent in comparison. WAY-214156 may produce anti-inflammatory effects via the ERò and has been proposed as a potential treatment for inflammatory conditions such as rheumatoid arthritis.