Cinnabarinic acid is an endogenous kynurenine metabolite formed from oxidative dimerization of 3-hydroxyanthranilic acid and transamination of 3-hydroxykynurenine. Cinnabarinic acid activates glutamate receptors by interacting with residues of the glutamate binding pocket of mGlu4. Cinnabarinic acid induces apoptosis in T cells through generation of reactive oxygen species, the loss of mitochondrial membrane potential and caspase activation.