Rituximab for treatment of immune thrombocytopenia and thrombotic thrombocytopenic purpura

Abstract

Although immune thrombocytopenia (ITP) and thrombotic thrombocytopenic purpura (TTP) appear similar, their symptoms differ. The number of domestic patients diagnosed with ITP and TTP annually has been estimated to be around 24,000 and 400, respectively. Moreover, no major differences in the incidence rate, age of onset, and prognosis have been observed between Europe, the United States (US), and Japan. Both ITP and acquired TTP are autoimmune diseases that require immunosuppressive therapy, though lethal TTP requires the use of plasma exchange in combination with immunosuppression. In Europe and the US, the monoclonal antibody rituximab has been widely used for ITP and TTP since approximately 10 years ago. However, no public health insurance indication has been available for rituximab in Japan. For this reason, investigator-initiated clinical trials were conducted. As a result, rituximab had subsequently been indicated for ITP in 2017. Meanwhile, TTP was designated as an intractable disease in Japan in 2015, and the first clinical practice guidelines were published in 2017. A single-arm study involving rituximab was conducted on high-risk patients in whom treatment with five plasma exchanges was ineffective or ADAMTS13 inhibitor was >2 BU/ml. Approval for the new indication of rituximab for acquired TTP is expected in 2019.