4CPS-072 Real-world experience in haemophilia B patients after switching to fix extended half-life using pharmacokinetic population software and monocompartmental model

Background and ImportanceNew strategies have been developed for the prophylactic treatment of patients with haemophilia B (HB) such as extended half-life recombinant factor IX concentrates (rFIX EHL). These products have shown favourable pharmacokinetic properties, attaining a half-life 3- to 5-fold longer in rFIX EHL compared to standard FIX concentratesAim and ObjectivesEfficiency of a pharmacokinetic-based tailored prophylaxis-dosing schedule versus standard dosing (DS) is compared, in HB, treated with two rFIX-EHL.Material and MethodsObservational, analytical, prospective, multicentre study, involving HB patients, being treated with rFIX-EHL linked to albumin (rFIX-FP) or to fragment crystallisable (rFIX-Fc). Demographic and clinical data, and DS and dosing interval (DI) and actual FIX trough levels were recorded. Pharmacokinetic characterisation was performed following both a population (WAPPS-HEMO) and a linear one-compartment (OC) approach. For each approach and rFIX preparation, an estimation of the time to the target trough (5 IU FIX/dL) was made. Statistical analysis was performed by means of the Student-Fisher t-test.ResultsFifteen patients were included, nine being treated with rFIX-FP (mean age, 33 years; weight 60 kg), and six with rFIX-Fc (49 years, 86 kg). Mean DS was 3222 UI (SD, 1716) every 11,9 days (SD, 4,4) for rFIX-FP patients; and 4333 UI (SD, 606) every 14,0 days (SD, 0,0) for rFIX-Fc patients. The individual tailored DI, for a 0,05 UI/dL trough target was: applying OC; 13,6 days (SD, 5,1), -1,8 days (SD, 5,9) vs DS, representing 240 IU/day (SD, 136,1) for rFIX-FP (p=0,40), and 8,6 days (SD, 1,2), +5,4 days (SD, 1,2) vs DS, representing 508 IU/day (SD, 65,6), for rFIX-Fc, (p