Photo courtesy of Biogen
A recombinant factor IX Fc fusion protein (rFIXFc) has produced favorable results in children with severe hemophilia B, researchers have reported.
The team said rFIXFc was generally well-tolerated in the phase 3 Kids B-LONG study, and none of the patients on this trial developed inhibitors.
In addition, the annualized bleeding rate was low, and most patients were able to maintain once-weekly dosing.
“To date, Kids B-LONG is the largest study to evaluate the safety and efficacy of extended half-life factor IX therapy in children with hemophilia B, and the study’s results align with those in studies of [rFIXFc] in adults and adolescents,” said Roshni Kulkarni, MD, of Michigan State University in East Lansing.
Dr Kulkarni and her colleagues reported results of Kids B-LONG in The Lancet Haematology. The research was funded by Biogen and Sobi, the companies marketing rFIXFc (also known as eftrenonacog alfa) as Alprolix.
The study included 30 males under the age of 12 with previously treated, severe hemophilia B.
All patients initially received rFIXFc prophylaxis (50-60 IU/kg) once per week. Doses were adjusted as needed (≤100 IU/kg per infusion, up to 2 times per week).
Twenty-seven patients (90%) completed the study. The median time spent on study was 49.4 weeks, and 24 patients received rFIXFc injections on at least 50 separate days.
None of the patients developed inhibitors to rFIXFc. There were no reports of anaphylaxis or serious hypersensitivity reactions, no vascular thrombotic events, and no deaths.
The most common adverse events were common cold (n=7, 23%) and fall (n=6, 20%). Four patients experienced serious adverse events while on study, all of which were considered unrelated to rFIXFc.
The median annualized bleeding rate was 2.0 overall, and there were no spontaneous joint bleeds.
Of all 30 patients treated, 10 (33%) experienced no bleeding episodes, and 19 (63%) reported no joint bleeding on-study.
Overall, 92% of bleeding episodes were controlled by 1 or 2 injections of rFIXFc.
Following a switch to rFIXFc, 80% of children who completed the study (22/27) extended their dosing interval compared to previous treatment.
One patient had his dosing interval reduced to 5 days, but all other patients remained on once-weekly prophylactic dosing throughout the study.
