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J Med Chem. 2012 Feb 23;55(4):1490-9. doi: 10.1021/jm201177b. Epub 2012 Feb 7.

3-aryl-[1,2,4]triazino[4,3-a]benzimidazol-4(10H)-one: a novel template for the design of highly selective A₂B adenosine receptor antagonists.

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Dipartimento di Scienze Farmaceutiche, Università di Pisa, Via Bonanno 6, 56126 Pisa, Italy.


In an effort to identify novel ligands possessing high affinity and selectivity for the A(2B) AR subtype, we further investigated the class of 3-aryl[1,2,4]triazino[4,3-a]benzimidazol-4(10H)-ones V, previously disclosed by us as selective A(1) AR antagonists. Preliminary assays on a number of triazinobenzimidazoles derived from our "in-house" collection revealed that all the derivatives selected showed significant affinity at A(2B) AR, no affinity at A(3) AR, and various degrees of selectivity toward A(1) and A(2A) ARs. Investigation of a new series featuring modified substituents at the 10-position (4'-chlorophenyl or phenylethyl groups), and a chlorine atom at the 7-position (X) of the triazinobenzimidazole nucleus, yielded highly potent and selective A(2B) AR antagonists. The presence of a pendant 3-phenyl ring appears to hamper the interaction with A(2A) AR, conferring high A(2B)/A(2A) AR selectivity. Derivative 13 (X = Cl, R = C(6)H(5)) is the most potent and selective compound, with an IC(50) of 3.10 nM at A(2B) AR and no affinity at A(1), A(2A), and A(3) ARs.

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