The present invention relates to novel compounds and formulations thereof which compounds are ligands, e.g., agonists or antagonists, for a metabotropic glutamate receptor or a NAALADase enzyme or both. The present invention also relates to methods of modulating the activity of a metabotropic glutamate receptor or a NAALADase enzyme or both, e.g., in a subject in need thereof, using a compound or formulation of the present invention. The present invention also relates to methods of treating a subject suffering from a chronic or acute disease, malady or condition due at least in part to an abnormality in the activity of an endogenous metabotropic glutamate receptor or a NAALADase enzyme or both, using a compound or formulation of the present invention.