Extending recombinant factor IX Fc fusion protein dosing interval to 14 or more days in patients with hemophilia B

Abstract

BackgroundIn the phase 3 B‐LONG study (NCT01027364), prophylaxis with recombinant factor IX Fc fusion protein (rFIXFc) every 7 to >14 days was associated with low annualized bleed rates (ABRs) in males aged ≥12 years with severe hemophilia B. The long‐term safety and efficacy of rFIXFc prophylaxis was confirmed in the B‐YOND study (NCT01425723), an extension of the B‐LONG clinical trial. ObjectiveThe aim of this post‐hoc analysis was to evaluate the efficacy of a ≥14‐day rFIXFc dosing interval in patients treated prophylactically during B‐LONG or B‐YOND. MethodsThe analysis included 22 patients aged ≥12 years who received prophylactic rFIXFc with a ≥14‐day dosing interval at any time during B‐LONG or B‐YOND up until the second interim analysis of B‐YOND (September 2015). ResultsThe median (interquartile range [IQR]) rFIXFc exposure on the ≥14‐day dosing interval was 3.4 (1.8‐4) years. Patients treated with a ≥14‐day dosing interval were well controlled with a median (IQR) overall ABR of 1.6 (0.6‐2.7) and a median (IQR) spontaneous ABR of 0.7 (0.3‐1.1) in 18 evaluable patients. A rFIXFc dosing interval of ≥14 days was well tolerated, with no new safety concerns identified. ConclusionMost patients on rFIXFc prophylaxis, with a dosing interval of ≥14 days, remained well controlled; ABRs were consistent with those reported in the overall study population. A ≥14‐day dosing interval can be utilized in some well controlled individuals and reduces the burden imposed by frequent prophylactic injections while maintaining adequate bleed suppression.