Pharmacotherapy for schizophrenia has limitations such as residual positive and negative symptoms, cognitive deficits and intolerable side effects. Refractory schizophrenia (particularly clozapine-resistant) is still a difficult clinical issue at present. Among schizophrenia patients, around 20-25%are treatment-resistant. According to the N-methyl-D-aspartate (NMDA) hypothesis, many clinical trials on NMDA-enhancing agents were studied. Adjuvant NMDA-enhancing agents, including glycine, D-amino acids (D-serine, D-alanine), and sarcosine (a glycine transporter I inhibitor), revealed beneficial but limited efficacy for positive and negative symptoms. The investigators recently started to study the potential of DAAOI-1, a D-amino acid oxidase (DAAO) inhibitor which can elevate synaptic concentration of D-amino acids.
The aims of this project is to examine the effectiveness and safety of DAAOI-1 adjuvant treatment for clozapine-resistant refractory schizophrenia patients in a randomized, double-blind, placebo - controlled trial.
