Safety and efficacy of nonacog alfa for the treatment of haemophilia B in children younger than 6 years of age in a routine clinical care setting: the EUREKIX registry study

Introduction: European regulatory authorities request postmarketing safety and efficacy data for factor IX (FIX) products. Aim: Collect additional clinical data from routine nonacog alfa use in children aged <6 years with haemophilia B. Methods: The EUREKIX registry included retrospective and prospective data collection phases. Safety was assessed via adverse drug reactions (ADRs)/adverse events (AEs) and events of special interest (ESIs) as the primary objective; efficacy was evaluated via annualised bleeding rates (ABRs). Results: The retrospective phase comprised 37 subjects. Of these, 25 had severe haemophilia B. One subject experienced 2 ADRs; another experienced 4 ESIs of hypersensitivity. Median ABR in subjects receiving a predominantly on-demand regimen (prophylaxis <50% of time; n = 11) was 2.0; median ABR was 3.8 in those receiving predominantly prophylactic treatment (prophylaxis ≥50% of time; n = 24). Joint bleeding was infrequent (median ABR, 0.4; n = 35). The prospective phase included 26 subjects, with 17 continuing from the retrospective phase. A total of 20 subjects had severe haemophilia B. Three subjects experienced 7 treatment-related AEs; 3 experienced 4 ESIs. Median ABR was 4.5 and 1.1 in subjects who received predominantly on-demand (n = 5) or prophylactic treatment (n = 19), respectively; the overall median ABR for joint bleeding events was 0.0. Conclusions: Overall, nonacog alfa treatment effectively controlled bleeding events, with no new safety signals identified. These data support the safety and efficacy of nonacog alfa in routine clinical settings in children aged <6 years.