An antagonist of EP4 (IC50 70 nM) selective for EP4 over EP1 EP2 and EP3 in a cAMP reporter assay at 10 UM reduces differentiation of mouse helper T cells at 0 1 to 10 nM and decreases IL-23 secretion by mouse dendritic cells at 0 04 to 5 nM reduces MDV levels in CEFs at 1 UM prevents and reverses paw swelling edema and inflammation at 30 and 100 mg/kg in a mouse model of rheumatoid arthritis induced by GPI