Favorable pharmacokinetics in hemophilia B for nonacog beta pegol versus recombinant factor IX‐Fc fusion protein: A randomized trial

BACKGROUND AND OBJECTIVE: Nonacog beta pegol (N9‐GP) and recombinant factor IX‐Fc fusion protein (rFIXFc) are extended half‐life rFIX compounds. We report the first single‐dose pharmacokinetic trial of N9‐GP and rFIXFc. PATIENTS/METHODS: Paradigm 7 was a multicenter, open‐label, randomized, crossover trial in previously treated (>150 exposure days) adults with congenital hemophilia B (FIX activity ≤2%). Patients received single intravenous injections (50 IU/kg) of N9‐GP and rFIXFc with at least 21 days between doses. Plasma FIX activity, predose, and at serial time points up to 240 hours postdose, was measured using validated one‐stage clotting assays (SynthAFax for N9‐GP; Actin FSL for rFIXFc) and a chromogenic assay (ROX factor IX) with normal human plasma as calibrator. The primary endpoint was area under the FIX activity–time curve from 0 to infinity, dose‐normalized to 50 IU/kg (AUC(0‐inf,norm)). RESULTS: Fifteen patients received study treatment. Based on FIX activity results from the one‐stage clotting assays, estimated AUC(0‐inf,norm) was significantly greater for N9‐GP than rFIXFc (ratio: 4.39; P < 0.0001, based on a two‐sided test on 5% significance level). In addition, N9‐GP had a longer terminal half‐life, two times higher incremental recovery at 30 minutes and maximum FIX activity (dose‐normalized to 50 IU/kg) and six times higher FIX activity at 168 hours than rFIXFc. These findings were largely comparable with the chromogenic assay data and are consistent with published data for each compound. CONCLUSIONS: In this comparison, N9‐GP demonstrated favorable pharmacokinetic characteristics versus rFIXFc, helping clinicians to understand differences between N9‐GP and rFIXFc. REGISTRATION: This trial is registered with clinicaltrials.gov (NCT03075670) and the European Clinical Trials Database (EudraCT: 2016‐001149‐25).