N6-Cyclopentyl-2-(3-phenylaminocarbonyltriazene-1-yl)adenosine (TCPA), a Very Selective Agonist with High Affinity for the Human Adenosine A1 Receptor
- 18 March 2003
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of Medicinal Chemistry
- Vol. 46 (8) , 1492-1503
- https://doi.org/10.1021/jm021074j
Abstract
Four subtypes of adenosine receptors are currently known, that is, A1, A2A, A2B, and A3 receptors. Interestingly, quite substantial species differences exist especially between human and rat A3 receptors. As a result, ligands such as CCPA, which are very selective for the rat A1 receptor versus the human A3 receptor, are substantially less selective when the human A1 and A3 receptors are compared. New 2-substituted and 2,N6-disubstituted adenosines were synthesized, and their affinities for the human adenosine A1, A2A, A2B, and A3 receptors were determined. Although large substituents on the C2-position are generally thought to yield adenosine A2A receptor selective ligands, the reported series of 2-triazeno-substituted adenosines had a very high affinity for the A1 receptor. For example, 2-(3-phenylaminocarbonyltriazene-1-yl)adenosine had an affinity of 6.1 ± 1.3 nM for the human adenosine A1 receptor. Introduction of a diphenethyl substituent at the N6-position of this compound resulted in a high-affinity agonist, 3.1 ± 0.9 nM, for the human adenosine A1 receptor with 316- and 45-fold selectivity versus the human A2A and human A3 receptors, respectively. The most selective, high-affinity human adenosine A1 receptor agonist was the disubstituted compound N6-cyclopentyl-2-(3-phenylaminocarbonyltriazene-1-yl)adenosine (TCPA). TCPA had an affinity of 2.8 ± 0.8 nM for the human adenosine A1 receptor and was 75-fold and 214-fold selective versus the human A2A and human A3 receptors, respectively. In addition, TCPA was a full agonist and inhibited the forskolin-induced cAMP production of CHO cells stably transfected with the human adenosine A1 receptor with an IC50 of 1.5 ± 0.5 nM.Keywords
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