Safety and Efficacy of Recombinant Fusion Protein Linking Coagulation Factor IX with Albumin (rIX-FP) in Previously Untreated Patients with Hemophilia B

• Published in: TH open : companion journal to thrombosis and haemostasis 2024-01, Vol.8 (1), p.e155-e163
• Main Authors: Lemons, Richard, Wang, Michael, Curtin, Julie, Lepatan, Lynda Mae, Male, Christoph, Peyvandi, Flora, von Depka Prondzinski, Mario, Wang, Rongrong, McKeand, William, Seifert, Wilfried, Oldenburg, Johannes
• Format: Article
• Language: English
• Subjects: factor IX; hemophilia B; Original; pediatric; previously untreated patients; prophylaxis
• ISSN: 2512-9465; 2567-3459; 2512-9465
• DOI: 10.1055/s-0044-1781466

Recombinant fusion protein linking coagulation factor IX (FIX) with albumin (rIX-FP) has been shown to be an effective, well-tolerated treatment for patients with severe hemophilia B who had previously received factor replacement therapy. This study investigated the safety and efficacy of rIX-FP in previously untreated patients (PUPs).  Patients with moderately severe/severe hemophilia B (≤2% FIX) previously untreated with FIX replacement products received rIX-FP (25-75 IU/kg) prophylaxis weekly or on-demand treatment over ≥50 exposure days (EDs). Primary outcomes were the number of patients who developed FIX inhibitors and mean incremental recovery (IR) following a 50 IU/kg dose of rIX-FP. Secondary outcomes included incidence of adverse events (AEs) and annualized bleeding rates (ABRs).  In total, 12 PUPs with a median age of 0 years (range, 0-11 years) were treated with rIX-FP for a median of 50 EDs (6/12 prophylaxis; 6/12 on-demand then prophylaxis). Overall, 11/12 patients did not develop FIX inhibitors; one 11-year-old patient developed an inhibitor against FIX after 8 EDs and was ultimately withdrawn. Mean (standard deviation) IR was 1.2 (0.4,  = 8) (IU/dL)/(IU/kg). Of the 137 treatment-emergent AEs recorded, five were attributed to rIX-FP. On the prophylaxis regimen, median ABR was 1.0 (range, 0-3.9,  = 12). No thromboembolic events or deaths occurred during the study.  This study provides data to support the safety and efficacy of rIX-FP in PUPs requiring on-demand or prophylactic treatment for moderately severe/severe hemophilia B, consistent with results in previously treated patients. Overall, 1/12 patients developed an inhibitor against FIX.