Efficacy and Safety of Rituximab in Adult Patients with Idiopathic Relapsed or Refractory Thrombotic Thrombocytopenic Purpura (TTP). Results of a Spanish Multicenter Study.

Background: Therapeutic plasma exchange (PE) is the mainstay of treatment of thrombotic thrombocytopenic purpura (TTP). In many patients, prolonged PE is required to achieve remission and between 30% and 60% of patients relapse after a variable period of months to years, with a further episode of TTP or a chronic picture of recurrent relapses. Various immunosuppressive agents have been used in acute refractory and chronic relapsing cases. Despite advances in treatment, mortality remains at 15–20%. Limited clinical data from small groups of patients suggest that the administration of anti-CD20 antibody (Rituximab) may also be useful in acute refractory and chronic relapsing TTP. However, whether rituximab could be and effective strategy for adults with relapsed or refractory TTP remains unresolved.

Patients and Methods: We have studied the clinical response to rituximab in 22 adult patients (16 F/6 M; median age, 43 years, range 24–72) from 11 Spanish centers who presented with acute refractory (13 cases) or an acute relapse (9 cases) episode of idiopathic TTP. Second-line therapies previously administered included vincristine (11 cases) and splenectomy (2 cases). At the time of the study, five (28%) patients presented neurological symptoms, three (17%) renal failure, and two (17%) fever. On admission, every patient received daily PE and corticosteroids during the acute episode.

Results: Rituximab was administered a median of 16 days (range, 7–53) after starting PE. It was administered immediately after PE at a dose of 375 mg/m² each week for a median (range) of 4 (1–8) doses. No severe acute or delayed toxicity associated with rituximab was observed. Two (9%) patients died due to TTP-related causes 24 and 48 hours after relapse and were not evaluable for response. The remaining 20 (91%) patients achieved complete remission in a median of 21 days after initiating rituximab (range, 2–35). After a median follow-up of 13 months (range, 1.5–33), 17 patients are in remission and 3 patients have relapsed at 7, 29, and 29 months after rituximab administration.

Conclusion: Based on these results, rituximab appears a safe, effective, targeted therapy associated with a high response rate in adult patients with acute refractory/relapsing idiopathic TTP.