Caplacizumab Treatment for Acquired Thrombotic Thrombocytopenic Purpura In acquired thrombotic thrombocytopenic purpura (TTP), an immune-mediated deficiency of the von Willebrand factor–cleaving protease ADAMTS13 allows unrestrained adhesion of von Willebrand factor multimers to platelets and microthrombosis, which result in thrombocytopenia, hemolytic anemia, and tissue ischemia. Caplacizumab, an anti–von Willebrand factor humanized, bivalent variable-domain-only immunoglobulin fragment, inhibi