In phase 3 randomised, double-blind, placebo-controlled trial, B-cell depletion using several infusions of rituximab over 12 months was not associated with clinical improvement in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
Researchers from Haukeland University Hospital in Norway randomly assigned 151 adults with ME/CFS to receive either placebo or rituximab during the study period. Participants received treatment or sham infusion two weeks apart, followed by four maintenance infusions at three, six, nine and 12 months. Over two years of follow-up, the researchers looked for improved fatigue scores and self-reported function.
In contrast to preliminary observations in phase 1 and 2 trials, no statistically significant difference was observed between groups in any measure.
Overall response rates were 35.1 per cent in the placebo group and 26.0 per cent in the rituximab group (difference, 9.2%; 95% CI -5.5% to 23.3%; P=.22). The treatment groups did not differ in fatigue score over 24 months (difference in average score 0.02; 95% CI -0.27 to 0.31; P=.80) or any of the secondary endpoints. Twenty patients in the rituximab group and 14 in the placebo group had serious adverse events.
The authors say the results, published in the Annals of Internal Medicine, weaken the case for rituximab in treating ME/CFS.