Apimostinel (INN) (developmental code names NRX-1074, AGN-241660) is a novel antidepressant, acting as a selective partial agonist of an allosteric site of the glycine site of the NMDA receptor complex, which is under investigation by Naurex (recently acquired by Allergan) for the treatment of major depressive disorder. Its mechanism of action and effects are similar to those of rapastinel (GLYX-13), which is under development as an adjunctive therapy for treatment-resistant depression also by Naurex; however, apimostinel is 100-fold more potent by weight and, unlike rapastinel (which must be administered via intravenous injection), is orally-active. Apimostinel is intended by Naurex as an improved, follow-up drug to rapastinel. The drug has shown rapid antidepressant effects in pre-clinic