N-Acetyl-D-serine is the modified amino acid D-Serine (S270975). D-Serine is a neurotransmitter that is concentrated in the mammalian brain, and is one of the very few amino acids that occur in the D- and L-configurations in significant amounts. D-Serine is an potent agonist of the N-methyl-D-aspartate (NMDA) receptor in the brain, which is associated with schizophrenia. Use of D-Serine has been considered as an additional therapy for refractory schizophrenic patients.