Rituximab for the treatment of acquired antibodies to factor VIII.

BACKGROUND AND OBJECTIVES: Rituximab, a monoclonal chimeric antibody to the CD20 antigen, is an effective therapy for the treatment of non-Hodgkin's lymphomas. Moreover, rituximab has also shown to be effective in various autoimmune diseases including spontaneous antibodies to factor VIII. The aim of this study was to assess the efficacy of rituximab treatment of spontaneous inhibitors to factor VIII. DESIGN AND METHODS: We studied the efficacy of rituximab by analyzing the data of 42 previously published cases as well as one so far unpublished case. For comparison, we also analyzed 44 patients treated with cyclophosphamide/prednisone reported in the literature.
RESULTS: Treatment with rituximab resulted in an overall rate of complete remission (CR) of 78.6%. Similar results were found when analyzing patients who had (75%) or had not (77%) received previous treatment with other immunosuppressive drugs. The median time to CR was 8.3 weeks. In follow-up 66% of the patients were still in CR after 2 years and the plateau in the Kaplan-Meier analysis suggests that a substantial number of patients had been cured. Among the 44 patients treated with cyclophosphamide/prednisone reported in the literature, the CR-rate was 84.1%, which was slightly higher than that for rituximab. The median time to CR with cyclophosphamide/prednisone treatment was 6.3 weeks, which was similar to that in the rituximab-treated patients; the probability of continuous CR at 2 years was 94%. INTERPRETATION AND
CONCLUSIONS: All in all, both treatment schemes are effective therapies in patients with spontaneous antibodies to factor VIII. Our data analysis is only descriptive and no conclusions can be drawn as to the relative efficacy of the two regimens. However, these data may serve as a useful basis for planning randomized studies to definitively resolve these issues.