Even as xenotropic murine leukemia virus-related virus has been taken off the table as a cause of chronic fatigue syndrome, new research from a Norwegian group points to the condition as a B cell disorder and suggests the potential to repurpose Rituxan rituximab and other CD20 antibodies. Indeed, the team reported that Rituxan, an anti-CD20 antibody, improved fatigue symptoms in a Phase II/III trial.1
The origins of the trial date back to 2003, when physicians at Haukeland University Hospital diagnosed a CFS patient with Hodgkin's lymphoma. Over the next several years the patient received four different chemotherapy regimens, one of which included methotrexate, an inhibitor of folate metabolism also known to deplete B cells.2
Only the methotrexate-containing regimen improved the patient's CFS symptoms including fatigue, headaches and muscle pain.3 Because some CFS patients exhibit abnormalities in B cells and other immune cells,4 the Haukeland team hypothesized that the patient's improvement resulted from methotrexate's B cell inhibition.