UPF-523 (AIDA), a rigid (carboxyphenyl) glycine derivative, is a relatively potent and selective antagonist of group I metabotropic glutamate receptors (mGlu1a) with an IC50 of 214 μM. But UPF-523 has no effect on group II (mGlu2), group III (mGlu4) receptors or ionotropic glutamate receptors. UPF-523 has the potential for the research of the acute arthritis.