Selective Activation of Adenosine A2A Receptors on Immune Cells by a CD73-Dependent Prodrug Suppresses Joint Inflammation in Experimental Rheumatoid Arthritis

Adenosine A2A receptor (A2AR) agonists are both highly effective anti-inflammatory agents and potent vasodilators. To separate these two activities, we have synthesized phosphorylated A2AR agonists (prodrugs) that require the presence of ecto-5′-nucleotidase (CD73) to become activated. In the model of collagen-induced arthritis, 2-(cyclohexylethylthio)adenosine 5′-monophosphate (chet-AMP), but not 2-(cyclohexylethylthio)adenosine (chet-adenosine), potently reduced inflammation as assessed by fluorine-19 ( 19 F) magnetic resonance imaging and by histology. The prodrug effect was blunted by inhibition of CD73 and A2AR. The selectivity of drug action is due to profound up-regulation of CD73 and adenosine A2AR expression in neutrophils and inflammatory monocytes as found in recovered cells from the synovial fluid of arthritic mice. Plasma chet-adenosine was in the subnanomolar range when chet-AMP was applied, whereas concentrations required for vasodilation were about 100 times higher. Thus, chet-AMP is a potent immunosuppressant with negligible vasodilatory activity. These data suggest that phosphorylated A2AR agonists may serve as a promising new group of drugs for targeted immunotherapy of inflammation.