B-lymphocyte Depletion Using Rituximab in Chronic Fatigue Syndrome/ Myalgic Encephalopathy (CFS/ME). A Randomized Phase-III Study.

Selfreported Fatigue score is registered every second week, as the mean score for the four symptoms: "Post-exertional malaise", "Fatigue", "Need for rest", "Daily functioning" (scale 0-6). Mean Fatigue scores for the time intervals 0-4, 4-8, 8-12, 12-16, 16-20, 20-24 months are recorded for each patient. These data are used for statistical analysis. The difference in course of Fatigue score during 24 months follow-up, between the rituximab and placebo groups, will constitute the primary endpoint.

Overall response is recorded as the effect on CFS/ME symptoms during 24 months follow-up. The overall response is not predefined to a specific time interval, but is defined as mean Fatigue score at least 4.5 for at least 8 consecutive weeks for moderate response, and mean Fatigue score at least 5.0 for at least 8 consecutive weeks for major response. Single response periods and the sum of response periods during 24 months follow-up will be recorded.

SF-36 (ver 1.2) are selfreported by patients at baseline, and at 3, 6, 9, 12, 15, 18, 21 and 24 months follow-up. Changes in Physical health summary score, Physical function, and "Mean of five subdimensions" (Physical function, Bodily pain, Vitality, Social function, General health) are recorded. The difference in course during 24 months follow-up, between the rituximab and placebo groups, will constitute secondary endpoints.

Also, the difference between rituximab and placebo groups, in changes from baseline to recording at 18 months, for Physical health summary score, Physical function, and "mean of five SF-36 subdimensions", constitute secondary endpoints.

The patients' physical activity level, in a home setting for 7 consecutive days, is recorded using Sensewear armbands, with registration at baseline and repeated in the time interval 17-21 months follow-up. Changes from baseline to analysis during the time interval 17-21 months, for mean number of steps per 24h, maximum number of steps per 24h, mean duration per 24h with activity level at least 3.5 METs, max duration per 24h with activity level at least 3.5 METs, are recorded. The difference between rituximab and placebo groups will constitute secondary endpoints.

Self-recorded "Function level" (scale 0-100, compared to healthy state, according to a set of examples) are registered every second week. Mean "Function level" for the time intervals 0-4, 4-8, 8-12, 12-16, 16-20, 20-24 months are calculated. The difference in course of "Function level", between the rituximab and placebo groups, constitute a secondary endpoint.

Also, the differences between the rituximab and placebo groups, for changes in selfreported "Fatigue score" and in selfreported "Function level", calculated from baseline to the mean value during the time interval 16-20 months, constitute secondary endpoints.

Fatigue Severity Scale (FSS) is self-recorded at baseline and at 6, 12, 18, 24 months. The difference between the rituximab and placebo groups, in changes in FSS from baseline to 18 months follow-up, constitutes a secondary endpoint.

Clinical response periods, defined as consecutive self-recorded Fatigue score at least 4.5 (scale 0-6) for a minimum of 8 weeks, during 24 months follow-up, are recorded.

The difference in the longest consecutive clinical response period, between rituximab and placebo groups, constitutes a secondary endpoint.

The difference between rituximab and placebo groups, in fraction of patients with sustained clinical response (defined as Fatigue score of at least 4.5) at 24 months, constitute a secondary endpoint.

Toxicity and side effects will be recorded throughout 24 months follow-up, as specified in the protocol.