Schizophrenia is a condition that causes symptoms like delusions, hallucinations, reduced motivation and muddled thinking. It is a common, severe and disabling psychiatric illness affecting about 1/100 (1%) of people. It is ranked the third most disabling illness worldwide. Six in seven patients do not recover from the illness in 6-12 months and continue to experience psychotic symptoms. Therefore, there is a strong unmet need for new evidence-based treatments to target the neurobiology underlying schizophrenia. There is increasing evidence to indicate that glutathione (GSH), the main brain antioxidant, is abnormal in schizophrenia and may provide a new treatment target. In this study we plan to determine whether Diroximel Fumarate (DRF) (currently a treatment for a brain disorder called multiple sclerosis) can increase GSH in the brain of patients with schizophrenia using a brain scan (MRI) and explore whether changes in GSH are related to other brain measures (measured with MRI and EEG- which measures electrical activity in the brain), blood markers of GSH, and symptoms. During this study 30 people with schizophrenia will be recruited. They will take the drug DRF for two weeks, a computer will then decide randomly whether each person will continue to take DRF or a placebo/dummy pill for another two weeks. During this part of the study neither the patients nor the researchers will know which type of drug the patient is taking. Brain GSH and the other measures described will be assessed before and after taking the DRF and placebo/dummy pill. At the end of the study (2027), we will see if taking DRF alters the brain chemical (GSH) in people with schizophrenia and whether this is linked to other measures and symptoms. It will also give researchers information about the best way to design future studies for patients with schizophrenia using this drug.