Document resource
Background and Importance Extended half-life (EHL) factor IX (FIX) prolongs circulation time compared with standard half-life (SHL) products, potentially enhancing protection and reducing infusion burden for patients with haemophilia B (HB). However, real-world evidence on pharmacokinetic (PK)-guided switching is still limited.Aim and Objectives To evaluate changes in PK parameters, clinical outcomes and cost during the first year after PK-guided switch from SHL to EHL FIX in patients with severe/moderate HB on prophylaxis.Material and Methods Multicentre, observational, retrospective, and multidisciplinary study conducted from December 2024 to May 2025 comparing pharmacokinetic and clinical outcome variables 1 year before and after the switch, including associated costs. Clinical data – annualised total bleeding rate (ABR), annualised joint bleeding rate (AJBR), weekly dose (IU/kg − 1), infusion frequency – were extracted from OrionClinic. PK profiles and PK variables – half-life, area under the curve (AUC), trough levels – were obtained using WAPPS-Hemo, whereas economic data (Laboratory Purchase Price without Value-Added Tax) were obtained from Orion-Logis. Quantitative variables were expressed as median (IQR) and qualitative as n (%). Statistical analysis was performed with R.v.4.4.3.Results Twenty-one patients (nine paediatric, 12 adults) were included in the study. All PK parameters showed significant improvement, with median improvement ratios for t1/2 and AUC of 4.1 (3.4–4.8) and 4.2 (2.6–5.0), respectively, with no age group differences (p>0.05). ABR was significantly reduced (p = 0.009), with resolution of 5 out of 6 (83.3%) target joints. Infusion frequency and weekly dose were reduced by 50.0% (50–65%; p = 0.0001) and 56.3% (40.0–65.8%; p = 0.0001), respectively, with a median reduction of 52.1 (26.1–67.8) injections and 130,357.3 (5,142.9–203,357.3) IU of FIX per patient per year. Despite lower consumption, the median annual drug cost increased to €28,254.9 (4,432.1–44,060.8) per patient per year.Conclusion and Relevance PK-guided switching to EHL FIX prophylaxis markedly improved all PK parameters while reducing treatment burden and improving both efficacy and quality of life in patients with HB. Although our analysis did not demonstrate direct cost savings—as only drug-related expenses were considered—this contrasts with haemophilia A, where switching to EHL factors has shown significant economic benefits. Comprehensive real-world studies including indirect costs are warranted to better define the full health-economic impact of EHL FIX therapy.Conflict of Interest No conflict of interest