AMT-061 is being developed by uniQure as a gene therapy for hemophilia B patients. The product uses an adeno-associated virus as a vector to deliver the highly active Padua factor IX (fIX) variant, which has eightfold to ninefold greater activity than normal, wild-type fIX. The gene therapy was previously investigated in a Phase II trial as AMT-060, although the updated product has two nucleotide substitutions in the coding sequence, resulting in the Padua variant. This will theoretically allow for sustained, therapeutic clotting factor levels at a low vector dose.
Following discussions with the US Food and Drug Administration and European Medicines Agency, AMT-061 retains the same regulatory incentives granted to AMT-060, which will expedite its path to market.
AMT-061 appears to be some way behind SPK-9001 (Spark Therapeutics/Pfizer) in a direct comparison of the clinical data generated so far. Not only was AMT-061’s biological efficacy weaker, with lower fIX activity, but patients still experienced spontaneous bleeds and required additional clotting factor treatment. Indeed, uniQure’s largest clinical trial was for AMT-060, which encoded for a different fIX amino acid sequence. However, by incorporating the Padua fIX variant in AMT-061, uniQure expects to have a more competitive gene therapy that can offer higher and more stable fIX expression and consequently greater bleed prevention.
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