title: D-serine for the treatment of negative symptoms in individuals at clinical high risk of schizophrenia: a pilot, double-blind, placebo-controlled, randomised parallel group mechanistic proof-of-concept trial.
abstract: BACKGROUND
  Antagonists of N-methyl-D-aspartate-type glutamate receptors (NMDAR) induce symptoms that closely resemble those of schizophrenia, including negative symptoms. D-serine is a naturally occurring NMDAR modulator that reverses the effects of NMDAR antagonists in animal models of schizophrenia. D-serine effects have been assessed previously for treatment of established schizophrenia, but not in the early stages of the disorder. We aimed to assess effects of D-serine on negative symptoms in at risk individuals.
  
  
  METHODS
  We did a double-blind, placebo-controlled, parallel-group randomised clinical trial at four academic US centres. Individuals were eligible for inclusion in the study if they were at clinical high risk of schizophrenia, aged between 13-35 years, had a total score of more than 20 on the Scale of Prodromal Symptoms (SOPS), and had an interest in participation in the clinical trial. Exclusion criteria included a history of suprathreshold psychosis symptoms (ie, no longer qualifying as prodromal) or clinical judgment that the reported symptoms from the SOPS were accounted for better by another disorder (eg, depression). Randomisation was done using a generated list with block sizes of four. Participants were stratified by site, with participants, investigators, and assessors all masked through use of identical looking placebos and centralised drug dispensation to study assignment. D-serine (60 mg/kg) was given orally in divided daily doses for 16 weeks. The primary endpoint was for negative SOPS, measured weekly for the first 6 weeks, then every 2 weeks. Participants who received at least one post-baseline assessment were included in analysis. Serum cytokine concentrations were collected at baseline, midpoint, and endpoint to assess the mechanism of action. Safety outcomes including laboratory assessments were obtained for all individuals. This trial is registered with ClinicalTrials.gov, number NCT0082620.
  
  
  RESULTS
  We enrolled participants between April 2, 2009, and July 23, 2012. 44 participants were randomly assigned to receive either D-serine (n=20) or placebo (n=24); 35 had assessable data (15 D-serine, 20 placebo). D-serine induced a 35·7% (SD 17·8) improvement in negative symptoms, which was significant compared with placebo (mean final SOPS negative score 7·6 [SEM 1·4] for D-serine group vs 11·3 [1·2] for placebo group; d=0·68, p=0·03). Five participants who received D-serine and nine participants who received placebo discontinued the study early because of withdrawn consent or loss to follow-up (n=8), conversion to psychosis (n=2), laboratory-confirmed adverse events (n=2), or protocol deviations (n=2).
  
  
  CONCLUSIONS
  This study supports use of NMDAR-based interventions, such as D-serine, for treatment of prodromal symptoms of schizophrenia. On the basis of observed effect sizes, future studies with sample sizes of about 40 per treatment group would be needed for confirmation of beneficial effects on symptoms and NMDAR-related inflammatory changes. Long-term studies are needed to assess effects on psychosis conversion in individuals at clinical high risk of schizophrenia.
  
  
  BACKGROUND
  National Institutes of Health.
authors.affiliation: Schizophrenia Research Center, Nathan Kline Institute, Orangeburg, NY, USA; Department of Psychiatry, Columbia University, New York, NY, USA.
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Kantrowitz
authors.affiliation: Department of Psychiatry, Yale University and Connecticut Mental Health Center, New Haven, CT, USA.
authors.forename: Scott W
authors.initials: SW
authors.lastname: Woods
authors.affiliation: Schizophrenia Research Center, Nathan Kline Institute, Orangeburg, NY, USA; Department of Child and Adolescent Psychiatry, New York University School of Medicine, New York, NY, USA.
authors.forename: Eva
authors.initials: E
authors.lastname: Petkova
authors.affiliation: Department of Psychiatry, Zucker Hillside Hospital, Glen Oaks, NY, USA.
authors.forename: Barbara
authors.initials: B
authors.lastname: Cornblatt
authors.affiliation: Department of Psychiatry, Columbia University, New York, NY, USA.
authors.forename: Cheryl M
authors.initials: CM
authors.lastname: Corcoran
authors.affiliation: Department Biostatistics, University of Florida, Gainesville, FL, USA.
authors.forename: Huaihou
authors.initials: H
authors.lastname: Chen
authors.affiliation: Schizophrenia Research Center, Nathan Kline Institute, Orangeburg, NY, USA.
authors.forename: Gail
authors.initials: G
authors.lastname: Silipo
authors.affiliation: Schizophrenia Research Center, Nathan Kline Institute, Orangeburg, NY, USA; Department of Psychiatry, Columbia University, New York, NY, USA. Electronic address: javitt@nki.rfmh.org.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Javitt
mesh_terms: D000293:Adolescent; D000328:Adult; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D018570:Risk Assessment; D012559:Schizophrenia / Q000503:physiopathology* / Q000517:prevention & control*; D012694:Serine / Q000627:therapeutic use*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D016194:Receptors, N-Methyl-D-Aspartate; D012694:Serine