The arrestin transcriptional output data (Figure ) indicates that at all physiologically relevant concentrations WinterGreen-WAY is inactive for arrestin recruitment. The assay was then run in antagonist mode by adding a fixed (1uM) concentration of test compound and observing changes to the curve of the control agonist. Upon incubation with WinterRed-NDMC as the test compound, the curve of our WAY-161503 control was not shifted, indicating WinterRed-NDMC is inactive as an antagonist for 5HT2C. The parent pharmacophores were measured for the first time using this assay. The EC50 for WAY-161503 was significantly higher than presently reported literature values, at 316 nM versus 12 nM in literature. There is limited data reporting EC50 values for WAY-161503, so the discrepancy is likely due one of two reasons, (1) the current data on WAY-161503 binding at the 5HT2C receptor is too limited to assign a definitive value (2) modulation of the secondary β-arrestin pathway may possess different characteristics than the current values which were derived from radiolabeled competition assay. ) is indicated to be inactive for 5HT2C antagonism at physiologically relevant concentrations.