Abstract We have disclosed a series of 1-benzyl-3-ketoindole derivatives acting as either positive or negative modulators of the human A 2B adenosine receptor (A 2B AR) depending on small differences in their side chain. The new compounds were designed taking into account structural similarities between AR antagonists and ligands of the GABA A/benzodiazepine receptor. All compounds resulted totally inactive at A 2A and A 3 ARs ...