B-Lymphocyte Depletion in Myalgic Encephalopathy/ Chronic Fatigue Syndrome. An Open-Label Phase II Study with Rituximab Maintenance Treatment. — CFSMEATLAS
B-Lymphocyte Depletion in Myalgic Encephalopathy/ Chronic Fatigue Syndrome. An Open-Label Phase II Study with Rituximab Maintenance Treatment.
Fluge, Øystein, Risa, Kristin, Lunde, Sigrid et al. · PloS one · 2015 · DOI
Quick Summary
This study tested whether removing B-cells (immune cells) using a drug called rituximab could help ME/CFS patients. Twenty-nine patients received rituximab infusions over 15 months and were followed for 3 years. Eighteen patients (62%) showed lasting improvement in fatigue, with some staying better for over 2 years, though improvements took several months to appear.
Why It Matters
This study provides evidence that B-cell depletion may produce sustained clinical benefits in a subgroup of ME/CFS patients, suggesting a potential autoimmune mechanism underlying the disease. The findings support further investigation into immunological pathways and could eventually lead to targeted treatments for patients who don't respond to conventional therapies.
Observed Findings
Eighteen of 29 patients (62%) showed major or moderate clinical responses lasting a mean of 105 weeks (major) and 69 weeks (moderate).
Eleven of 18 responding patients remained in clinical remission at 36-month follow-up.
Mean time to clinical response was 23 weeks after first rituximab infusion (range 8-66 weeks).
Six patients from the prior placebo group achieved clinical response within 12 months after rituximab maintenance infusions.
Adverse events were limited: 2 allergic reactions, 2 late-onset neutropenia cases, and 8 transient symptom flares.
Inferred Conclusions
Prolonged B-cell depletion with maintenance rituximab infusions is associated with sustained clinical responses in a subgroup of ME/CFS patients.
The delayed response pattern and relapse after B-cell regeneration suggest ME/CFS may involve autoimmune mechanisms similar to other B-cell-mediated conditions.
The three-fold higher disease prevalence in women and previously documented increased B-cell lymphoma risk in elderly ME/CFS patients support an autoimmune disease hypothesis.
Remaining Questions
Which patient characteristics or biomarkers predict response to rituximab, and can responders be identified before treatment?
What This Study Does Not Prove
This open-label study cannot definitively prove rituximab causes improvement because there was no control group receiving placebo alongside the treatment phase—expectation effects cannot be excluded. The study does not establish that all ME/CFS patients will benefit, nor does it identify which patient characteristics predict response. Long-term safety beyond 3 years remains unknown.