A ligand-based pharmacophore was obtained for a new series of 2-unsubstituted and 2-(para-substituted)phenyl-pyrazolo-triazolo-pyrimidines as potent human A(3) adenosine receptor antagonists. Through comparative molecular field analysis-based quantitative structure-activity relationship studies, structural features at the N(5)-, N(8)- and C(2)-positions of the tricyclic nucleus were deeply investigated, with emphasis given to the unprecedentedly explored C(2)-position. The resulting model showed good correlation and predictability (r(2)=0.936; q(2)=0.703; r(pred)(2)=0.663). Overall, the contribution of steric effect was found relatively more predominant for the optimal interaction of these antagonists to the human A(3) receptor.
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