[Novel treatment strategies for acquired thrombotic thrombocytopenic purpura].

Thrombotic thrombocytopenic purpura (TTP) is a poor prognosis disease caused by platelet thrombi produced in the microvessels throughout the body. The thrombus is mainly composed of von Willebrand factor (VWF) and platelets. Acquired TTP is an autoimmune disease wherein autoantibodies against ADAMTS13, a VWF-cleaving enzyme, are produced and ADAMTS13 activity is markedly decreased. Plasma exchange using fresh-frozen plasma as a replacement fluid effective against acquired TTP was reported in 1991. Since then, plasma exchange and corticosteroids have been the standard of care in Japan. Caplacizumab, which is a monoclonal antibody against the VWF A1 domain, finally became available for use in 2022, and the number of cases is still increasing in Japan. A clinical trial of recombinant ADAMTS13 product is being conducted for congenital TTP, and an era is expected to come in the future when plasma exchange will no longer be necessary.