B-cell Depletion Using the Monoclonal Anti-CD20 Antibody Rituximab in Very Severe Chronic Fatigue Syndrome

Based on pilot patient observations, and experience from the prior study KTS-1-2008, the investigators anticipate that severely affected chronic fatigue syndrome patients may benefit from B-cell depletion therapy using Rituximab induction with maintenance treatment. The hypothesis is that at least a subset of chronic fatigue syndrome (CFS) patients have an activated immune system involving B-lymphocytes, and that prolonged B-cell depletion may alleviate symptoms. An approved amendment (April 15th 2011): the study will be extended with up to 5 patients. For up to 5 patients in the study, standard plasma exchange may be performed 2-3 weeks prior to start of B-lymphocyte depletion using Rituximab (as in the protocol). Approved amendment (December 2011): for patients with gradual improvement in CFS/ME symptoms after 12 months follow-up, but not having reached a clear response, up to 6 additional Rituximab infusions (500 mg/m2, max 1000 mg) may be given during the following 12 months period.