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Wolfgang Miesbach: Second-Longest Follow-Up of Intravenous AAV Gene Therapy in Hemophilia B

Wolfgang Miesbach/LinkedIn

Feb 14, 2026, 14:07

Wolfgang Miesbach: Second-Longest Follow-Up of Intravenous AAV Gene Therapy in Hemophilia B

Wolfgang Miesbach, Professor of Medicine at Frankfurt University Hospital, shared on LinkedIn:

“Very happy to share data from my EAHAD2026 oral presentation on behalf of the co-authors, reporting the second longest follow‑up for intravenous AAV‑based gene therapy in haemophilia B.

CSL220 is the intravenous AAV5‑based predecessor of etranacogene dezaparvovec, and these 9‑year results provide rare long‑horizon evidence on durability of factor expression after a single infusion:

FIX activity remained stable, supporting durable transgene expression almost a decade after gene transfer.
Annualised bleeding rates stayed low in both cohorts, with spontaneous treated bleeds becoming rare in years 6–9.
Exogenous FIX consumption fell by >90% versus pre‑gene‑therapy levels, and importantly, no participant returned to continuous FIX prophylaxis over 9 years.
Long‑term safety was favourable: no FIX inhibitors, no thrombotic events, no late liver toxicity and no AAV‑related oncogenicity were observed, including in year 9.

With a 10‑year extension underway, this second‑longest AAV follow‑up reinforces that durable factor IX expression, sustained bleed protection and profound reductions in FIX use are achievable with a single intravenous gene therapy.”

Wolfgang Miesbach: Second-Longest Follow-Up of Intravenous AAV Gene Therapy in Hemophilia B