UniQure has released updated results from an ongoing Phase IIb study illustrating sustained therapeutic levels of Factor IX (FIX) in patients with haemophilia B three months after administration of its experimental AAV5-based gene therapy AMT-061.

The gene therapy was associated with mean FIX activity of 38% of normal at 12 weeks after administration in patients with severe and moderately severe forms of the bleeding disorder.

The drug is an AAV5-based gene therapy that contains a FIX-Padua variant, meaning a patent-protected form of Factor IX, the missing or insufficient protein that results in the disease.

Three patients with severe hemophilia, whose FIX activity was less than 1%, were enrolled. They received a single intravenous dose of the therapy.

At 16 weeks, the first patient had 48% of normal levels. FIX activity in the second patient was 25% at week 14, and the third patient had 51% of normal at 12 weeks. The second and third patients were excluded from another gene therapy earlier because of pre-existing neutralising antibodies to a different AAV vector.

“Our goal with AMT-061 is to give all people living with hemophilia B access to a one-time treatment capable of normalizing FIX activity and eliminating the need for replacement therapy, without the risk of immune responses that require immunosuppression or may lead to a loss of efficacy,” stated Matt Kapusta, chief executive officer of UniQure.

“These updated data continue to suggest that AMT-061 may be the first gene therapy able to achieve this goal, and we remain focused on completing enrollment in our ongoing pivotal Phase III study by the end of the year.”

Patients in the Phase IIb study will be followed for 52 weeks to assess FIX activity, bleeding rates and usage of FIX replacement therapy, and will be monitored for five years to evaluate the safety of AMT-061.