Probing distal regions of the A2B adenosine receptor by quantitative structure-activity relationship modeling of known and novel agonists.

The binding modes at the A 2B adenosine receptor (AR) of 72 derivatives of adenosine and its 5'- N-methyluronamide with diverse substitutions at the 2 and N (6) positions were studied using a molecular modeling approach. The compounds in their receptor-docked conformations were used to build CoMFA and CoMSIA quantitative structure-activity relationship models. Various parameters, including different types of atomic charges, were examined. The best statistical parameters were obtained with a joint CoMFA and CoMSIA model: R (2) = 0.960, Q (2) = 0.676, SEE = 0.175, F = 158, and R (2) test = 0.782 for an independent test set containing 18 compounds. On the basis of the modeling results, four novel adenosine analogues, having elongated or bulky substitutions at N (6) position and/or 2 position, were synthesized and evaluated biologically. All of the proposed compounds were potent, full agonists at the A 2B AR in adenylate cyclase studies. Thus, in support of the modeling, bulky substitutions at both positions did not prevent A 2B AR activation, which predicts separate regions for docking of these moieties.