Safety and efficacy of investigator-prescribed BeneFIX prophylaxis in children less than 6 years of age with severe haemophilia B.

Summary.  Prophylaxis is increasingly prescribed in treatment of haemophilia and its benefit is believed to be most significant for the youngest patients as haemophilic arthropathy may be prevented if prophylaxis is initiated prior to recurrent haemarthroses. While clinical prophylaxis data are readily available for haemophilia A, analogous data for haemophilia B are relatively limited. A prospective clinical study of recombinant factor IX (BeneFIX®; rFIX), designed to allow investigator prescribed prophylaxis according to customary practices, was conducted in children <6 years old with severe haemophilia B. Nearly all children were prescribed prophylaxis (22/25; 88%) for all or part of their study participation. Favourable efficacy and safety profiles were reported. Routine prophylaxis with 1 or 2 rFIX infusions per week over an average of greater than 6 months of therapy resulted in near complete prevention of spontaneous breakthrough haemorrhages (<1 per year), with most children (77%) having none, including seven patients (32%) who had no bleeding episodes at all. Haemorrhages in joints were less common than those outside joints (27% vs. 73% of haemorrhages). In a patient population that included children with multiple prior haemarthroses, 68% of children had no joint bleeding. Breakthrough haemorrhages resolved with 1 or 2 infusions in 89% of episodes. The absence of changes in prophylaxis infusion schedules suggests that 1 or 2 rFIX infusion(s) per week were well-tolerated by these young patients, including those with (41%) and without (59%) central venous access devices. Safety was established by the low incidence of treatment-related adverse events.