A Canadian phase II study evaluating the efficacy of rituximab in the management of patients with relapsed/refractory thrombotic thrombocytopenic purpura.

Rituximab is a chimeric monoclonal antibody that targets the human CD-20 antigen present on malignant and normal B lymphocytes. Recent clinical studies have shown a significant response rate when this drug is given to selected patients with thrombotic thrombocytopenic purpura (TTP). Given that the clinical manifestations of TTP may be the direct result of an auto-antibody against a regulatory Von Willebrand factor enzyme (ADAMTS13), it makes biological sense to consider a therapy that has the ability to diminish or eradicate antibody-producing B cells. Despite initial positive results, there is a need to identify which patients derive durable benefit from this agent. As in other conditions that utilize therapeutic immunosuppression, there is a risk that the addition of rituximab may also lead to serious opportunistic infections.