The US Food and Drug Administration (FDA) has approved a recombinant factor IX Fc fusion protein (rFIXFc, Alprolix) for use in adults and children with hemophilia B.
The product is intended to help control, prevent, or reduce the frequency of bleeding episodes that can occur day-to-day in patients with hemophilia B, as well as manage bleeding in patients undergoing surgery.
rFIXFc is made by fusing factor IX to the Fc portion of the IgG1 protein. Scientists believe this enables the product to use a naturally occurring pathway to prolong the time the therapy remains in the body.
The FDA’s approval is the second worldwide approval of rFIXFc. The product was recently authorized for use in Canada.
Researchers evaluated the safety, efficacy, and pharmacokinetics of rFIXFc in the phase 3 B-LONG study, which was funded by the product’s developers, Biogen Idec and Sobi.
Investigators tested rFIXFc in 123 males with hemophilia B who were at least 12 years of age. The patients were assigned to 1 of 4 treatment arms: weekly prophylaxis, individualized-interval prophylaxis, on-demand treatment to control bleeding, and perioperative management.
The overall median annualized bleeding rates were 2.95 for the weekly prophylaxis arm, 1.38 for the individualized-interval prophylaxis arm, and 17.69 in the on-demand treatment arm.
The overall median dosing interval with individualized-interval prophylaxis was 12.5 days. During the last 6 months of the study, the median dosing interval was 13.8 days.
Of the patients who received rFIXFc for perioperative management, 85.7% required a single injection of the product to maintain hemostasis during their operation. The median dose was 90.9 IU/kg per injection.
Most patients required 1 to 2 injections of the product the day before and the day of surgery. And most required 2 to 3 injections from days 1 to 3 after surgery.
The most common adverse events associated with rFIXFc (an incidence of ≥ 5% in a pooled analysis of treatment arms 1, 2, and 3) were nasopharyngitis, influenza, arthralgia, upper respiratory tract infection, hypertension, and headache.
The results of this study were released by Biogen Idec and Sobi in September 2012, presented at ISTH 2013, and published in NEJM in December 2013.
