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Wolfgang Miesbach: How Should We Monitor FVIII Expression After AAV5-Based Gene Therapy?
Wolfgang Miesbach/LinkedIn
Jun 3, 2026, 09:14

Wolfgang Miesbach: How Should We Monitor FVIII Expression After AAV5-Based Gene Therapy?

Wolfgang Miesbach, Professor of Medicine at Frankfurt University Hospital, shared a post on LinkedIn about a recent article by Flora Peyvandi et al, published in Journal of Thrombosis and Haemostasis, adding։

“How should we monitor FVIII expression after AAV5-based gene therapy (valoctocogene roxaparvovec)?

In 4 adults with severe haemophilia A treated with a single infusion of valoctocogene roxaparvovec, the authors collected 182 plasma samples over a median of 61 weeks.

Measurement of FVIII activity using:

  • one-stage clotting assay (OSA)
  • chromogenic substrate assay (CSA)
  • FVIII antigen using an ELISA specifically optimised for B‑domain–deleted FVIII (the transgene product)

What they found:

  • The one-stage assay (OSA) consistently reported around 1.6–2.0 higher FVIII activity than the chromogenic assay (CSA) across follow-up.
  • FVIII antigen levels showed a strong correlation with chromogenic FVIII activity, suggesting that the CSA more accurately reflects the functional expression of the AAV5-delivered FVIII transgene.
  • The combined use of FVIII activity (CSA) and FVIII antigen provided a coherent picture of transgene expression, synthesis and secretion over time.

For haemophilia centres implementing post–gene therapy monitoring algorithms, these data support:

  • Using the chromogenic FVIII assay (CSA) as the primary functional readout after AAV5 FVIII gene therapy
  • Adding FVIII antigen measurement to improve biological interpretation (e.g. distinguishing true biological changes from assay-related variability)

Congratulations to the authors on a very timely and practice-relevant contribution to post–gene therapy monitoring in haemophilia A.”

Title: Correlation between Factor VIII chromogenic activity and antigen levels in patients treated with adeno-associated virus 5-mediated gene therapy for hemophilia A

Authors: Flora Peyvandi, Isabella Garagiola,  Cristina Novembrino, Lucia Schiavone, Massimo Boscolo-Anzoletti, Alessandro Ciavarella, Vincenzo La Mura

Wolfgang Miesbach: How Should We Monitor FVIII Expression After AAV5-Based Gene Therapy?

Other posts featuring Wolfgang Miesbach on Hemostasis Today.

Alessandro Ciavarella bleeding disorders Cristina Novembrino Flora Peyvandi Health Hemophilia Hemostasis Hemostasis News Hemostasis Today Isabella Garagiola Lucia Schiavone Massimo Boscolo Anzoletti Medicine Vincenzo La Mura Wolfgang Miesbach
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