Rituximab for Schizophrenia Spectrum Disorder (RITS-PS-2019)

Immunological factors may be determinants for some psychiatric disorders, thus immunomodulation may be helpful. Rituximab (antibodies against CD20, cluster of differentiation), a standard treatment for multiple sclerosis, is an anti-inflammatory drug, hitherto not tested for psychiatric disorders. The aim of this study is to investigate whether the psychiatric symptoms of treatment-resistant adult psychiatric patients, diagnosed with schizophrenia spectrum disorder (SSD), are significantly improved after treatment with rituximab. Our purpose is to implement recent insights from "Immunopsychiatry" to find efficacious, but still tolerable treatment for these patients. This is a single-site, 20-week, open pilot, add-on treatment as usual, trial, where the patients will be followed for 1 year. Rituximab will be administered with one single dose of 1000 mg. Investigators will analyse inflammatory and metabolic biomarkers in relation to the primary outcome, treatment response (defined as clinically relevant reduction in the validated measure PANSS). Other outcomes are "much" or "very much improved" on Clinical Global Impression - Improvement scale (CGI-I) and change in Personal and Social Performance Scale measuring overall disability.