Immunological factors are assumed to be determinants for some psychiatric disorders, thus anti-inflammatory drugs may be helpful. However, studies on such treatments are scarce. Rituximab (anti-CD20 antibodies), a standard treatment for multiple sclerosis in Sweden, is an inflammatory modulating drug. In a small open pilot trial, markedly ill, treatment-resistant participants with schizophrenia spectrum disorder were treated with a single- dose rituximab (1000 mg), as add-on treatment to antipsychotics in Örebro, Sweden (2019-2022). Large improvements in all types of psychotic symptoms were evident, with long-lasting effects and few side-effects in most of the participants.~This is a proof-of-concept study based on our earlier findings. The investigators will conduct a multicenter, placebo-controlled, double-blinded, add-on intervention study for 104 participants with schizophrenia spectrum disorder (18-51 years). Sampling from blood for analyses of inflammatory mediators are investigated at gene and protein levels and rsfMRI and lumbar puncture are optional. Biomarkers will be investigated in relation to treatment response.~Participants are assessed at five time-points; week 0, 2, 7, 12 (endpoint I) and 24 (endpoint II).~Research questions:~I Does the addition of rituximab to standard psychiatric treatment improve psychotic symptoms in SSD?~II Does overall disability improve with the addition of rituximab?~III Are clinical or biological markers related to treatment response?~IV Is rituximab safe and well tolerated by participants with SSD?~In addition family member(s) to the patient will be asked to participate in a qualitative interview by a researcher after 3 months on changes in the patient's mood and anxiety level, general functioning, behaviours, energy level, psychotic symptoms, motivation, emotional reciprocity and insight to enable a qualitative analysis. We will also ask them about their general thoughts on the study.~We will also aim study changes in negative symptoms with the Motivation and pleasure- self report (MAP-SR) in addition to the Positive and Negative Syndrome Scale (PANSS) scale.
Immunological factors are assumed to be determinants for some psychiatric disorders, thus anti-inflammatory drugs may be helpful. However, studies on such treatments are scarce. An inflammatory modulating drug rituximab, cluster of differentiation antigen 20 antibodies (anti-CD20 antibodies), is a standard treatment for e.g. multiple sclerosis.~The investigators aim to test rituximab in a randomised placebo-controlled double-blinded, add-on treatment trial in 120 participants (18-55 years) with schizophrenia spectrum disorder. Sampling from blood for analyses of inflammatory mediators are investigated at gene and protein levels and resting state functional magnetic resonance imaging (rsfMRI) and lumbar puncture are optional. Biomarkers will be investigated in relation to treatment response.~Family member(s) to the patient will be asked to participate in a qualitative interview by a researcher after 3 months.