- The disease
- Haemophilia B is a rare inherited bleeding disorder caused by deficiency of factor IX (FIX), a protein required for normal blood clotting. People with the condition experience spontaneous or trauma-triggered bleeding episodes, particularly into joints and muscles, and have historically required lifelong intravenous replacement therapy to prevent and treat bleeds. The condition affects predominantly males and varies in severity depending on residual FIX activity levels.
- What the asset is trying to do
- Hemgenix is an adeno-associated virus serotype 5 (AAV5) gene therapy designed to deliver a functional copy of the FIX gene to liver cells, with the goal of enabling the body to produce its own FIX protein. The FIX transgene incorporates a gain-of-function variant (Padua variant) intended to increase FIX activity per molecule relative to wild-type FIX. Unlike standard FIX replacement products that require repeated infusions, Hemgenix is administered as a single intravenous infusion (per Hemgenix US prescribing information).
- What the trial is measuring, and why it matters
- The ongoing post-marketing study (NCT06008938) is an observational cohort study designed to characterise the long-term real-world effectiveness and safety of Hemgenix in patients with haemophilia B. It collects data on FIX activity levels, annualised bleeding rates, FIX product use, and safety events over time. Long-term follow-up data of this kind are a regulatory requirement for novel gene therapies given the absence of multi-decade clinical experience with the modality.
- Efficacy benchmarks in this setting
- In pivotal clinical programme data submitted to regulators, the approved benchmark for haemophilia B prophylaxis includes standard half-life and extended half-life (EHL) recombinant FIX products; EHL products such as eftrenonacog alfa (Alprolix) and nonacog beta pegol (Rebinyn) have demonstrated annualised bleeding rate reductions and are approved for routine prophylaxis (per respective US prescribing information). Emicizumab (Hemlibra), a bispecific antibody approved for haemophilia A (not B), is not a direct comparator. Early-stage or post-marketing observational figures for Hemgenix are not statistically comparable to controlled trial results from those approved therapies.
- Commercial context
- Hemgenix received US Food and Drug Administration (FDA) approval in November 2022 and European Medicines Agency (EMA) approval in February 2023, making it the first approved gene therapy for haemophilia B (per FDA and EMA approval records). CSL acquired the asset through its acquisition of uniQure's haemophilia B gene therapy programme; the financial terms of that transaction are publicly disclosed in CSL's regulatory filings. Hemgenix is listed as a commercial product within CSL Behring, CSL's biotherapeutics division. No further deal terms or manufacturing cost figures are included here, as none were provided in the input data.