Once-weekly prophylactic dosing of recombinant factor IX improves adherence in hemophilia B

Abstract

Regular prophylactic treatment in severe hemophilia should be considered an optimal treatment. There is no general agreement on the optimal prophylaxis regimen, and adherence to prophylaxis is a main challenge due to medical, psychosocial, and cost controversies. Improved approaches in prophylaxis regimen of hemophilia B are needed to make patients’ lives easier. There is some evidence to support the efficacy of once-weekly prophylaxis. Longer sampling schedules are required for the determination of pharmacokinetic (PK) properties of factor IX (FIX). The half-life of FIX seems to be longer than previously described and is expected to be 34 hours. The clinical significance of maintaining a 1% trough level is widely debated in hemophilia B. The overall relationship between factor concentrate levels and incidence of joint bleeding was found to be very weak. Data also indicate that the distribution of FIX into an extravascular FIX compartment may contribute to hemostasis independently of circulating plasma FIX levels. Clinical assessment of the frequency and severity of bleeds remain an important measure of the efficacy of treatment. Role of PK-guided therapy remains to be established. Two prospective randomized studies had evaluated the efficacy and safety of 100 IU/kg once-weekly prophylaxis with nonacog alfa, and this prophylaxis regimen was found to be associated with lower annual bleeding rate compared with on-demand treatment in adolescents and adults with moderately severeto- severe hemophilia B. Secondary prophylaxis therapy with 100 IU/kg nonacog alfa once weekly reduced annual bleeding rate by 89.4% relative to on-demand treatment. Residual FIX may be supportive of effectiveness. Once-weekly prophylaxis was well tolerated in the two studies, with a safety profile similar to that reported during the on-demand treatment period. To individually tailor treatment to clinical response and to minimize costs of factor concentrate, it would be of interest to investigate the efficacy of lower doses of the drug administered once a week.