Efficacy of rituximab in acute refractory or chronic relapsing non-familial idiopathic thrombotic thrombocytopenic purpura: a systematic review with pooled data analysis.

Idiopathic thrombotic thrombocytopenic purpura (TTP) occurs primarily due to the formation of autoantibody against ADAMTS13, a specific von Willebrand factor-cleaving protease, resulting in low ADAMTS13 activity and subsequent accumulation of large vWF multimers, platelet aggregation and thrombus formation in the microvasculature of tissues. Limited clinical data suggest that the administration of anti-CD20 antibody (rituximab) may be useful in treating acute refractory or chronic relapsing idiopathic TTP. We carried out a systematic review with pooled data analysis using individual patient data to evaluate the efficacy of rituximab in these settings. Fifteen case series and 16 case reports comprising 100 patients were eligible for the study. Median age was 39 years. Male constituted 31 % and female 69 %. Complete remission was seen in 98 %, non-response in 2 % and relapse after complete remission in 9 %. For patients with complete remission, median follow-up was 13 months. Median platelet recovery from the first dose of rituximab was 14 days. ADAMTS13 inhibitor positivity and severe ADAMTS13 deficiency were highly predictive of the response to rituximab, implying that these can be useful markers in predicting response to rituximab in acute refractory or chronic relapsing idiopathic TTP.