Results of a phase 3 study suggest a recombinant factor IX Fc fusion protein (rFIXFc, also known as eftrenonacog alfa and Alprolix) is a feasible treatment option for children with severe hemophilia B.
rFIXFc effectively prevented and treated bleeding episodes, patients did not develop inhibitors, and there were no serious adverse events related to treatment.
Sobi and Biogen Idec, the companies developing rFIXFc, recently announced these results from the now-complete Kids B-LONG study.
They said the successful completion of this study supports applications for pediatric indications in several regions and is an important step in seeking marketing authorization for rFIXFc in Europe.
Interim results of the Kids B-LONG study helped support the US approval of rFIXFc for use in children.
In Kids B-LONG, researchers tested rFIXFc in 30 previously treated children younger than 12 who had severe hemophilia B. Patients had at least 50 prior exposure days to factor IX therapies.
Twenty-seven patients (90%) completed the study. The median time spent on study was 49.4 weeks, and 24 participants received rFIXFc injections on at least 50 separate days.
Children who received rFIXFc prophylactically had an overall median annualized bleeding rate (ABR) of 1.97. The median ABR for spontaneous joint bleeds was 0.
Approximately 33% of patients did not experience any bleeding episodes. About 92% of bleeding episodes were controlled by 1 or 2 injections of rFIXFc.
None of the patients developed inhibitors to rFIXFc. The terminal half-life of the product was 66.5 hours for children under 6 and 70.3 hours for children ages 6 to 11.
Researchers said there were no treatment-related serious adverse events and no cases of serious allergic reactions or vascular thrombotic events. None of the patients discontinued the study due to an adverse event.
One adverse event—decreased appetite occurring in 1 patient—was considered related to rFIXFc treatment.
The pattern of treatment-emergent adverse events in this study was generally consistent with results seen in adolescents and adults in the phase 3 B-LONG study. Common adverse reactions in that study were headache and oral paresthesia.
Additional analyses of the Kids B-LONG study are ongoing, and detailed results will be presented at a future scientific meeting, according to Sobi and Biogen Idec.
