Validation of the 18 kiloDalton Translocator Protein (TSPO) as a Novel Neuroimmunodulatory Target

In multiple sclerosis (MS) cells of the immune system attack the brain causing tissue damage. In secondary progressive MS (SPMS) these repeated immune attacks have stopped but despite this new damage continues to appear. TSPO is a protein found in the brain and cells of the immune system, whose levels increase during MS. The investigators would like to know whether drugs that bind TSPO could dampen the immune responses in patients with SPMS. The investigators will be testing two drugs that affect TSPO; etifoxine and XBD173. Subjects with SPMS will be recruited from neurology clinics at hospitals associated with Imperial College Healthcare NHS Trust. Healthy volunteers will also be recruited in order to provide a comparison to these patients. The volunteers recruited will be invited to the clinical research facility (CRF) at Hammersmith Hospital. The volunteers will take one of the two drugs every day for 7 days. The researchers will perform blood tests before the first dose and after the last dose to investigate the effects of the drugs, including the expression of genes and immune cell activity. This will allow the researchers to explore which of the two drugs produces the greatest changes in the amount of TSPO in the blood in MS patients relative to healthy controls.