Anti–von Willebrand Therapy for Thrombotic Thrombocytopenic Purpura

Mortality from acquired thrombotic thrombocytopenic purpura (TTP) remains at 10% to 20%, despite treatment with plasma exchange and immunosuppression. Blocking the formation of vessel-occluding platelet aggregates by administering an inhibitor of von Willebrand factor might improve outcomes in this disorder.

To examine the safety and efficacy of caplacizumab, a monoclonal antibody that binds to the von Willebrand factor and blocks its interaction with platelets, investigators conducted an industry-supported, multicenter, randomized, placebo-controlled, phase II study of 75 patients with acquired TTP (mean age, 42 years; mean platelet count, 24,600/μL). Patients received plasma exchange plus either 10 mg of subcutaneous caplacizumab or placeb…