Licostinel (ACEA 1021) is a potent competitive antagonist at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. The robust efficacy of glycine/NMDA antagonists, such as ACEA 1021, in animal model of brain ischemia, together with good safety profile in animal models and in clinical trials, suggested that this class of NMDA antagonists should have good chance of success in the clinic as neuroprotectants. The clinical trial of ACEA 1021 for stroke was discontinued, mainly due to low solubility and lack of metabolism of the drug that led to the observation of crystals in the urine of some of the patients. In vivo ACEA 1021 reduced the rate of propagation of cortical spreading depression, an effect consistent with blockade of NMDA receptors. ACEA 1021 also decreased audiogenic myoclonus in resuscitated rats following cardiac arrest, and the minimum alveolar concentration for halothane, effects which suggest a reduction of excitatory amino acid neurotransmission. ACEA 1021 crosses the blood-brain barrier and blocks the pathophysiologic consequences of NMDA receptor overstimulation. It was neuroprotective with a favorable therapeutic window in models of transient and permanent cerebral ischemia, epilepsy and pain.