Effectiveness of caplacizumab in the first-line treatment for acquired thrombotic thrombocytopenic purpura: single center experience

Acquired thrombotic thrombocytopenic purpura (aTTP) is a very rare life-threatening disorder, which manifests as a profound thrombocytopenia, microangiopathic hemolytic anemia, renal insufficiency, neurological dysfunction, and other ischemic organ damage. It is caused by antibodies blocking ADAMTS13 metalloprotease. The current standard of the treatment is a triple combination consisting of therapeutic plasma exchange (TPE), immunosuppressive therapy, and caplacizumab, an anti-vWF nanobody. We retrospectively analyzed the medical records and management of three patients with newly diagnosed acute form of aTTP. Three Slovak female patients (mean age at onset 57 years) with severe anemia and thrombocytopenia, one with acute renal insufficiency and two with neurological symptoms were admitted to our institution for suspected aTTP. All patients had ADAMTS13 activity below 2%, laboratory signs of hemolysis, and the presence of ADAMTS13 antibodies. In our laboratory, we also examined the ultra-large high-molecular-weight vWF multimers. The patients were urgently indicated for TPE and high-dose immunosuppressive therapy. Shortly thereafter, caplacizumab was added to the treatment. In the following days platelet count stabilized, ADAMTS13 activity increased and biochemical parameters were gradually adjusted. Two patients experienced exacerbations and one patient experienced relapse of aTTP with mild thrombocytopenia and reduced ADAMTS13 activity, without thrombotic microangiopathy. They were successfully treated with rituximab or cyclophosphamide. Clinical remission was achieved later in all patients. Data collected from our center show that addition of caplacizumab to the standard aTTP treatment helps normalize platelet count faster, reduces the number of TPE sessions and length of hospitalizations, and significantly improves the clinical outcome of patients.