Long-Term Safety and Efficacy of Recombinant Coagulation Factor IX Albumin Fusion Protein (rIX-FP) in Previously Treated Pediatric Patients with Hemophilia B: Results from a Phase 3b Extension Study

Thromb Haemost. 2020 Apr;120(4):599-606. doi: 10.1055/s-0040-1705116. Epub 2020 Mar 17.

Abstract

Introduction: A phase 3b extension study evaluated the long-term safety and efficacy of a recombinant fusion protein-linking coagulation factor IX (FIX) with albumin (rIX-FP) for the routine prophylaxis and on-demand treatment of bleeding in pediatric hemophilia B patients.

Methods: Previously treated patients aged <12 years with moderate to severe hemophilia B enrolled in a 3-year extension study following a phase 3 pivotal study in which they received weekly rIX-FP prophylaxis. In the extension study, they could maintain or extend their prophylaxis interval to every 10 or 14 days if they were well controlled on the 7-day regimen.

Results: Compared with their initial regimen, by the end of the study, dosing intervals were the same, extended, and shortened in 16, 4, and 4 patients, respectively. Very low annualized spontaneous bleeding rates (AsBRs) were observed; median AsBR was 0.0 for the 7- and 10-day regimens, and 1.1 for the 14-day regimen. The 7- and 14-day regimens were comparable in preventing spontaneous bleeds; mean (95% confidence interval) difference in AsBR of -1.2 (-2.6 to 0.3) bleeding episodes/year/subject. Overall, 96% of bleeding episodes were successfully treated with one or two injections of rIX-FP. Patients on a 14-day regimen maintained a mean steady-state trough FIX level of >7.2 IU/dL. No patient developed an inhibitor.

Conclusion: This extension study demonstrated the long-term safety and efficacy of weekly rIX-FP in pediatric patients. Additionally, it showed that adequate bleed protection can be achieved with 10- or 14-day rIX-FP regimens in selected pediatric patients while maintaining safety.

Publication types

  • Clinical Trial, Phase III
  • Multicenter Study

MeSH terms

  • Albumins / genetics
  • Albumins / therapeutic use*
  • Child
  • Child, Preschool
  • Factor IX / genetics
  • Factor IX / therapeutic use*
  • Hemophilia B / complications
  • Hemophilia B / drug therapy*
  • Hemorrhage / etiology
  • Hemorrhage / prevention & control*
  • Humans
  • Male
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / therapeutic use*
  • Time Factors
  • Treatment Outcome

Substances

  • Albumins
  • Recombinant Fusion Proteins
  • Factor IX