Real?world outcomes with recombinant factor IX Fc fusion protein (rFIXFc) prophylaxis: Longitudinal follow?up in a national adult cohort

Introduction In 2017, all people with severe haemophilia B (PWSHB) in Ireland switched from standard half-life (SHL) recombinant FIX (rFIX) to rFIX Fc fusion protein (rFIXFc) prophylaxis. Aims To evaluate prophylaxis regimens, bleeding rates and factor usage for two years of rFIXFc a real-world setting. Methods Data collected retrospectively electronic diaries medical records PWSHB two-year period on were compared paired baseline data SHL treatment. Results 28 (?18 years) enrolled, at switchover 79% receiving 21% episodic treatment rFIX. At 24 months following switchover, remained reduced infusion frequency; median dose per once weekly (55 IU/kg, 20/28), every 10 days (63 2/28) or 14 (98 6/28). Median annualised bleed rate improved significantly (2.0 versus 3.3 FIX) (p = 0.01). trough level once-weekly infusions was 0.09 IU/ml (0.06–0.14 IU/ml). Management episodes similar rFIX; one sufficient treat 74% 77% bleeds, respectively, total episode. Factor consumption by 28% (57 IU/kg/week, range 40–86 IU/kg/week) (79 44–210 0.002). Conclusion This study provides important insights into experience switching an adult population, demonstrating high prophylaxis, frequency, consumption.