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Papers of the Week

2022 Apr 14

ACS Med Chem Lett



Selective A Adenosine Receptor Antagonist Radioligand for Human and Rodent Species.


Suresh RR, Gao Z-G, Salmaso V, Chen E, Campbell RG, Poe RB, Liston TE, Jacobson KA
ACS Med Chem Lett. 2022 Apr 14; 13(4):623-631.
PMID: 35450351.


The A adenosine receptor (AAR) is a target for pain, ischemia, and inflammatory disease therapy. Among the ligand tools available are selective agonists and antagonists, including radioligands, but most high-affinity non-nucleoside antagonists are limited in selectivity to primate species. We have explored the structure-activity relationship of a previously reported AAR antagonist DPTN (-[4-(3,5-dimethylphenyl)-5-(4-pyridyl)-1,3-thiazol-2-yl]nicotinamide) for radiolabeling, including 3-halo derivatives (3-iodo, MRS7907), and characterized as a high -affinity radioligand [H]MRS7799. AAR values were (nM): 0.55 (human), 3.74 (mouse), and 2.80 (rat). An extended methyl acrylate (MRS8074, ) maintained higher affinity (18.9 nM) than a 3-((5-chlorothiophen-2-yl)ethynyl) derivative . Compound had an excellent brain distribution in rats (brain/plasma ratio ∼1). Receptor docking predicted its orthosteric site binding by engaging residues that were previously found to be essential for AR binding. Thus the new radioligand promises to be a useful species-general antagonist tracer for receptor characterization and drug discovery.