Emicizumab for the treatment of acquired hemophilia A

Acquired hemophilia A (AHA) is a severe bleeding disorder caused by inhibiting autoantibodies to coagulation factor VIII (FVIII). For hemostatic treatment, bypassing agents and human or porcine FVIII are currently standard of care. Emicizumab is a bispecific, FVIII-mimetic therapeutic antibody that reduced the annualized bleeding rates in congenital hemophiliacs. Here, we report on 6 male and 6 female patients with AHA treated with emicizumab (all data medians and interquartile range), age 74 (64-80) years, initial FVIII <1%; inhibitor titer 22.3 Bethesda units (BU)/mL (range, 3-2000). Eight patients had severe bleeding. Emicizumab was started, 3 mg/kg subcutaneously, weekly for 2 to 3 doses, followed by 1.5 mg/kg every 3 weeks to keep the lowest effective FVIII levels. For FVIII monitoring, chromogenic assays with human and bovine reagents were used. All patients received immunosuppression with steroids and/or rituximab. After the first dose of emicizumab, activated partial thromboplastin time normalized in 1 to 3 days, FVIII (human reagents) exceeded 10% after 11 (7.5-12) days. Hemostatic efficacy was obtained and bypassing therapy stopped after 1.5 (1-4) days. FVIII (bovine reagents) exceeded 50%, indicating complete remission after 115 (67-185) days, and emicizumab was stopped after 31 (15-79) days. A median of 5 injections (range, 3-9) were given. No patient died of bleeding or thromboembolism, and no breakthrough bleeding was observed after the first dose of emicizumab. In conclusion, emicizumab seems to be an effective hemostatic therapy for AHA, with the advantages of subcutaneous therapy, good hemostatic efficacy, early discharge, and reduction of immunosuppression and adverse events.