Design and Characterization of an Intracellular Covalent Ligand for CC Chemokine Receptor 2

Covalently
acting inhibitors constitute a large and growing fraction
of approved small-molecule therapeutics as well as useful tools for
a variety of in vitro and in vivo applications. Here, we aimed to develop a covalent antagonist of
CC chemokine receptor 2 (CCR2), a class A GPCR that has been pursued
as a therapeutic target in inflammation and immuno-oncology. Based
on a known intracellularly binding CCR2 antagonist, several covalent
derivatives were synthesized and characterized by radioligand binding
and functional assays. These studies revealed compound 14 as an intracellular covalent ligand for CCR2. In silico modeling followed by site-directed mutagenesis confirmed that 14 forms a covalent bond with one of three proximal cysteine
residues, which can be engaged interchangeably. To our knowledge,
compound 14 represents the first covalent ligand reported
for CCR2. Due to its unique properties, it may represent a promising
tool for ongoing and future studies of CCR2 pharmacology.