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Synthesis and Application of the First Radioligand Targeting the Allosteric Binding Pocket of Chemokine Receptor CXCR3
Author(s) -
Bernat Viachaslau,
Heinrich Markus R.,
Baumeister Paul,
Buschauer Armin,
Tschammer Nuska
Publication year - 2012
Publication title -
chemmedchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.817
H-Index - 100
eISSN - 1860-7187
pISSN - 1860-7179
DOI - 10.1002/cmdc.201200184
Subject(s) - allosteric regulation , radioligand , chemistry , allosteric modulator , receptor , cc chemokine receptors , cxcr3 , chemokine receptor , biophysics , radioligand assay , stereochemistry , pharmacology , biochemistry , biology , chemokine
Strategies for the identification of allosteric modulators of chemokine receptors largely rely on various cell‐based functional assays. Radioligand binding assays are typically not available for allosteric binding sites. We synthesized, purified, and applied the first tritium‐labeled allosteric modulator of the human chemokine receptor CXCR3 (RAMX3, [ 3 H] N ‐{1‐[3‐(4‐ethoxyphenyl)‐4‐oxo‐3,4‐dihydropyrido[2,3‐ d ]pyrimidin‐2‐yl]ethyl}‐2‐[4‐fluoro‐3‐(trifluoromethyl)phenyl]‐ N ‐[(1‐methylpiperidin‐4‐yl)methyl]acetamide). RAMX3 is chemically derived from 8‐azaquinazolinone‐type allosteric modulators and binds to the CXCR3 receptor with a K d value of 1.08 n M (specific activity: 80.4 Ci mmol −1 ). Radioligand displacement assays showed potent negative cooperativity between RAMX3 and chemokine CXCL11, providing a basis for the use of RAMX3 to investigate other potential allosteric modulators. Additionally, the synthesis and characterization of a number of other full and truncated 8‐azaquinazoline analogues were used to validate the binding properties of RAMX3. We demonstrate that RAMX3 can be efficiently used to facilitate the discovery and characterization of small molecules as allosteric modulators of the CXCR3 receptor.