Comparison of the activity of C20-arylated vitamin D analogs 53-57 in the human PBMC IL-17 release assay identified several potent compounds, although a moderate overall loss in potency was observed compared to calcipotriol (7) (Figure ). In general, a clear difference in potency was observed between the two C20-stereoisomers of each arylated compound tested. Hence, (R)-53a showed an EC50 of 104 nM while the corresponding (S)-53b exhibited a complete loss of activity. (R)-54a, bearing a -OMe group, resulted in a 9-fold increase in potency compared to 53a, while its (S)-isomer counterpart in 54b showed only moderate activity. Interestingly in the case of the