AZD8529, a positive allosteric modulator at the mGluR2 receptor, does not improve symptoms in schizophrenia: A proof of principle study

Introduction: Activation of metabotropic glutamate (mGluR2/3) receptors has been proposed as an alternative mechanism to dopaminergic-based antipsychotics to correct glutamatergic deficits hypothesized to underlie schizophrenia symptoms. This study investigates the efficacy and safety of AZD8529, a selective positive allosteric modulator (PAM) at the mGlu2 receptor, in symptomatic patients with schizophrenia. Methods: Patients were randomized to receive AZD8529 40 mg, risperidone 4 mg, or placebo as monotherapy. Treatment lasted for 28 days, and clinical efficacy was assessed using Positive and Negative Syndrome Scale (PANSS) and Clinical Global Impression (CGI) scores. Results: There were no significant differences between patients treated with AZD8529 versus placebo in change from baseline to endpoint in PANSS total, negative and positive symptom subscale, or CGI-S scores. In contrast, risperidone demonstrated significant efficacy relative to placebo. Conclusion: These results do not support a role for the mGluR-2 PAM AZD8529 as an antipsychotic and indicate that positive modulation of mGluR type 2 receptors alone is not sufficient for antipsychotic effects in acutely ill schizophrenia patients. (C) 2016 Published by Elsevier B.V.