Approximately one third of patients with schizophrenia fail to respond to dopamine-blocking antipsychotic medications. While treatment resistant schizophrenia (TRS) is generally thought to be present from the onset of first episode psychosis (FEP), prospective identification of these patients remains clinically challenging. We investigated the association of glutamate, and glutathione with time to response in the anterior cingulate cortex (ACC) of minimally-treated patients with FEP (n=26) and healthy controls (n= 27) using an ultra-high field 7T MRI protocol. Higher ACC glutathione at baseline was associated with decreased time to achieve 50% symptom improvement. There were no significant differences between patients and controls on measures of glutamate, or glutathione. For the first time, we have demonstrated an association between glutathione and longitudinal treatment response. Interventions to increase brain glutathione may improve early treatment outcomes in patients with FEP