High adherence to prophylaxis regimens in haemophilia B patients receiving rIX-FP: Evidence from clinical trials and real-world practice

Introduction Adherence to prophylaxis regimens is essential for bleed prevention in haemophilia but remains a challenge due to the need for frequent infusions. Aim To evaluate patient adherence to prophylaxis regimens with a long-acting recombinant factor IX (rIX-FP; IDELVION® ) in clinical studies and real-world practice. Methods In two phase 3 clinical studies, patients with haemophilia B (FIX ≤2%) recorded their dose, dosing frequency and rIX-FP consumption in an e-diary. Adherence to prescribed prophylaxis regimens was assessed in all patients and to prescribed dose in patients ≥12 years only. Additionally, adherence to rIX-FP prophylaxis regimens in real-world practice was captured. Results In clinical studies, 94.9% (n = 56/59) of patients ≥12 years and 100% (n = 27) of paediatric patients received ≥80% of the expected number of infusions for their assigned prophylaxis schedule. Overall, mean adherence rate was 95.5% across all prophylaxis regimens in patients ≥12 years and 97.9% with a 7-day regimen in paediatric patients. In patients ≥12 years, 85.7% (n = 54/63) were dose adherent, defined as receiving within 10% of their prescribed dose ≥80% of the time. In real-world practice, adherence was observed in 100% (n = 14 and n = 15, respectively) of patients in two haemophilia treatment centres and 57.1% (n = 4/7) of patients in a third centre; non-adherence (n = 3/7) was linked to insurance-related and parental issues. Conclusion In clinical studies, patients with haemophilia B had high adherence rates to rIX-FP prophylaxis regimens with a variety of dosing intervals, enabling them to achieve very low bleeding rates. High adherence may also be achievable in real-world practice.