Rituximab in immune thrombocytopenia: transient responses, low rate of sustained remissions and poor response to further therapy in refractory patients.

Management of patients with immune thrombocytopenia (ITP) refractory to standard treatment is difficult. Recent studies show that rituximab, a chimeric anti-CD20 monoclonal antibody, is useful in the treatment of ITP. We retrospectively studied 24 patients who received 29 rituximab treatments for relapsed or refractory ITP. Patients had received a median of 3 treatment regimens before (range 1-8) and 11 patients had prior splenectomy. Responses were achieved in 19 of 29 (66%) treatments. The median time to response was 3 weeks (range 1-20) from the start of therapy and median duration of response was 13 weeks (range 1 week-55 months). Responses were mostly short lived and after a median follow-up of 22 months (range 2-70), 10 (34%) responses were sustained after 6 months, 7 (24%) responses sustained after 1 year and only 5 patients continued to have a response at last visit after 8, 10, 24, 30 and 54 months of follow-up. Previous splenectomy was associated with a poor response (p=0.034). Patients who failed rituximab and had prior multiple treatments including splenectomy, had a poor outcome of further therapies. We conclude that rituximab is well tolerated and is useful in some patients with relapsed or refractory ITP; however, only about one-fifth of patients achieved sustained remissions. Patients refractory to rituximab had a poor response to further treatment.