Development and Characterization of Potent Succinate Receptor Fluorescent Tracers

The succinate receptor (SUCNR1) has
emerged as a potential
target
for the treatment of various metabolic and inflammatory diseases,
including hypertension, inflammatory bowel disease, and rheumatoid
arthritis. While several ligands for this receptor have been reported,
species differences in pharmacology between human and rodent orthologs
have limited the validation of SUCNR1’s therapeutic potential.
Here, we describe the development of the first potent fluorescent
tool compounds for SUCNR1 and use these to define key differences
in ligand binding to human and mouse SUCNR1. Starting from known agonist
scaffolds, we developed a potent agonist tracer, TUG-2384 (22), with affinity for both human and mouse SUCNR1. In addition, we
developed a novel antagonist tracer, TUG-2465 (46), which
displayed high affinity for human SUCNR1. Using 46 we
demonstrate that three humanizing mutations on mouse SUCNR1, N181.31E, K2697.32N, and G84EL1W, are sufficient
to restore high-affinity binding of SUCNR1 antagonists to the mouse
receptor ortholog.