ORPHEE: A Real-World Study on rIX-FP Prophylaxis Use in Adolescent/Adult Patients With Hemophilia B

To assess the real-world efficacy and safety of recombinant factor IX albumin fusion protein (rIX-FP) in patients with hemophilia B (HB) in France. Data on dosing frequency, weekly consumption, and bleeds before-and-after switching to rIX-FP, were collected from December 2021 to February 2024. Annualized (spontaneous) bleeding rates [A(s)BRs] were calculated only in patients on prophylaxis with a follow-up ≥ 6 months. This interim analysis focused on 77 patients ≥ 12 years; 62 (81%) had severe HB. After switching to rIX-FP, the infusion interval was 14 (7-14) days. Weekly consumption was 43 (35.5-53) IU/kg. ABRs and AsBRs were 0.5 (0-1.9) and 0 (0-0.7) (n = 63) at 18.2 (12.3-21.9) months of follow-up. Prophylactic efficacy of rIX-FP was considered 'Excellent'/'Good' in 65/68 (95%) patients. Among the 43 patients previously treated with rFIXFc, 21 increased the infusion interval from 7 (7-11) days with rFIXFc to 14 (7-14) days with rIX-FP; 33/43 (77%) reduced weekly factor IX (FIX) consumption from 59.95 (46.35-77.93) to 42.5 (35.88-50.25) IU/kg. Patients maintained good protection against bleeds. This analysis confirmed that switching to rIX-FP allows for reducing injection frequency and FIX consumption while maintaining good bleed protection.