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.

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.
Competing Interests: G.K.: Research grant support from Alnylam, BPL, Bayer, Baxalta, CSL Behring, Opko biologics, Pfizer, Shire; consultant for Alnylam, Bayer, Opko biologics, Pfizer, Shire, Roche; honoraria/speakers bureau for Bayer, CSL, Pfizer, Roche. H.C.: Research support from CSL Behring, LFB, Novo Nordisk, Octapharma, Shire/Takeda, SOBI; honoraria from Bayer, LFB, Octapharma, Pfizer, Roche, SOBI; travel support from Bayer, LFB, Octapharma, Pfizer, Roche, Sobi; C.M.: Research support from Bayer, Biotest, CSL Behring, Shire/Takeda; honoraria from Bayer, Biotest, CSL Behring, Novo Nordisk, Pfizer, Roche, Takeda; travel support from Biotest, Bayer, CSL Behring, Novo Nordisk. S.H.: received honoraria for speaking from Bayer Healthcare, Baxalta Innovation, Biotest, CSL Behring, Novartis Pharma, Novo Nordisk, Octapharma, Pfizer; research grants from Bayer Healthcare, Baxalta, Biotest, CSL Behring, Novo Nordisk, Octapharma, Pfizer; T.L.: Research grant support and honoraria from Bayer, CSL Behring, Novo Nordisk, Octapharma, Pfizer, Roche, Shire, SOBI; honoraria from Uniqure; Y.L. and W.S. are employees of CSL Behring; E.S.: Research grant support from CSL Behring; honoraria for speaking and/or for consulting from Bayer, Bioverativ, CSL Behring, Grifols, Kedrion, Novo Nordisk, Octapharma, Pfizer, Roche, Shire/Takeda, SOBI, Spark, Uniqure.
(Georg Thieme Verlag KG Stuttgart · New York.)