GlycoPEGylated recombinant factor IX for hemophilia B in context

Nonacog beta pegol prophylaxis in children with hemophilia B: safety, efficacy, and neurodevelopmental outcomes for up to 8 years

Background

Nonacog beta pegol (N9-GP) is an extended half-life PEGylated factor (F)IX product with established efficacy and short-term safety in persons with hemophilia B (HB). Long-term safety has been evaluated for polyethylene glycol exposure but not N9-GP.

Objectives

To assess safety, neurodevelopmental, and efficacy outcomes of children with HB receiving N9-GP prophylaxis across 2 open-label, single-arm, phase 3 studies: paradigm5 (previously treated patients [PTPs]) and paradigm6 (previously untreated patients [PUPs]) in this interim analysis.

Methods

PTPs (aged ≤12 years) and PUPs (aged <6 years) with severe/moderate (≤2% FIX level) HB were recruited to N9-GP prophylaxis (40 IU/kg once weekly) in paradigm5 and paradigm6, respectively. Safety assessments included FIX inhibitor incidence, adverse events, neurocognitive and neurologic outcomes, polyethylene glycol concentration in plasma, and medical events of special interest. Efficacy endpoints included bleeds, N9-GP hemostatic effect, and FIX consumption.

Results

Overall, 25 patients in paradigm5 and 50 patients in paradigm6 received N9-GP and were followed for up to 8 and 6 years, respectively. No inhibitory antibodies were reported in PTPs; 4 of the 50 PUPs developed inhibitors. Extensive evaluation revealed no neurocognitive or neurologic concerns with N9-GP use in children during the study period. Across both studies, few adverse events were reported as possibly related to N9-GP. High hemostatic response rate, high treatment adherence, low annualized bleeding rates, and no new target joints were reported.

Conclusion

These data provide the longest follow-up for an extended half-life FIX and confirm the long-term efficacy of N9-GP prophylaxis in children with HB with no observed neurocognitive or neurologic safety concerns.

Current factor IX replacement options for hemophilia B and the challenges ahead

INTRODUCTION

Therapy for hemophilia B is aimed at replacing the congenital deficiency of coagulation factor IX (FIX). For replacement therapy, several FIX concentrates derived from donated human plasma or engineered by recombinant DNA technology are currently commercially available. The use of these products is well established and permit patients a relatively normal life. To further improve treatment efficacy, recombinant FIX products with a prolonged half-life have been developed, allowing relaxed prophylactic dosing and reducing treatment burden.

AREAS COVERED

In this review, we explore the current FIX replacement options for hemophilia B patients by analyzing the outcomes of their main clinical trials. We cover advances in the FIX molecules with extended half-life (EHL). Published literature on products for replacement of hemophilia B was retrieved using PubMed with no temporal limits.

EXPERT OPINION

The recent introduction of recombinant EHL FIX products has represented a major advance in the therapeutic management of hemophilia B patients, permitting both a reduction of treatment burden and improving patients' compliance to prophylaxis and, ultimately, quality of life.