Refining the standard of care in immune thrombotic thrombocytopenic purpura

Acute immune thrombotic thrombocytopenic purpura (iTTP) is a medical emergency. In the setting of any thrombotic microangiopathy (TMA), blood should be drawn to measure ADAMTS13 activity and inhibitor levels, and an assessment should be made of TTP risk before receiving ADAMTS13 results. This can include the use of PLASMIC and French scores. Plasma exchange (PE) is then initiated. Upon confirmation of iTTP, with ADAMTS13 less than 10% in the presence of an inhibitor, interventions targeting all facets of iTTP pathophysiology should be instituted: replenishing ADAMTS13 via continued PE; suppressing anti-ADAMTS13 autoantibodies with glucocorticoids and rituximab; and inhibiting the thrombotic process-uncontrolled formation of platelet/Von Willebrand factor (VWF) microthrombi-with caplacizumab. The latter, an addition to existing standards of care, is based on International Society on Thrombosis and Haemostasis guidelines and emphasizes tracking of ADAMTS13 activity. In HERCULES, a pivotal randomized controlled trial, caplacizumab use resulted in fewer recurrent iTTP episodes, decreased PE, and shortened hospital stay. In settings of high suspicion for iTTP, clinicians should consider the administration of caplacizumab before receiving ADAMTS13 results because the greatest benefits of caplacizumab accrued starting it within 3 days of TMA recognition. In HERCULES, serious bleeding events occurred among 11% of those in the caplacizumab group vs 1% in the placebo group, but all resolved, most without intervention. iTTP survivors receiving PE and immunosuppression alone are at a heightened risk for stroke, other cardiovascular disorders, neurocognitive impairment, and kidney disease. Whether rapid prevention of VWF multimer/platelet formation with caplacizumab can suppress such long-term sequelae, and whether caplacizumab can replace PE in initial therapy, are under investigation.