Real-world case series and summary of current literature of infants and toddlers with severe hemophilia A with inhibitor on prophylaxis with emicizumab.

Emicizumab is a recombinant, humanized, and a bispecific monoclonal antibody that bridges activated factor (F) IX and FX in place of FVIII to restore hemostasis in persons with hemophilia A (PHA). Data on the efficacy and safety of emicizumab in young children is limited. Immunologic naivety, physiologically decreased production of vitamin K dependent proteins, specifically FIX, and enhanced clearance of emicizumab in infants may support decreased emicizumab effectiveness. We report on the facilitation of care rendered by using emicizumab in young PHA with inhibitors and extend data on the efficacy and safety in PHA < 3 years.