Induction of ER Stress by an AAV5 BDD FVIII Construct Is Dependent on the Strength of the Hepatic-Specific Promoter.

Adeno-associated virus 5 (AAV5)-human factor VIII-SQ (hFVIII-SQ; valoctocogene roxaparvovec) is an AAV-mediated product under evaluation for treatment of severe hemophilia A, which contains a B-domain-deleted hFVIII (hFVIII-SQ) transgene and a hybrid liver-specific promotor (HLP). To increase FVIII-SQ expression and reduce the vector dose required, a stronger promoter may be considered. However, because FVIII-SQ is a protein known to be difficult to fold and secrete, this could potentially induce endoplasmic reticulum (ER) stress.

Prednisolone Does Not Regulate Factor VIII Expression in Mice Receiving AAV5-hFVIII-SQ: Valoctocogene Roxaparvovec.

AAV5-hFVIII-SQ (valoctocogene roxaparvovec) is an adeno-associated virus (AAV)-mediated gene therapy vector containing a B-domain-deleted human factor VIII (hFVIII-SQ) transgene. In a phase 1/2 clinical study of AAV5-hFVIII-SQ for severe hemophilia A (FVIII < 1 IU/dL), participants received prednisolone to mitigate potential immune-mediated reactions to the gene therapy and demonstrated concomitant elevations in plasma FVIII levels, following a single administration of AAV5-hFVIII-SQ. To assess whether prednisolone is capable of directly modulating transgene expression or levels of circulating hepatic enzymes, C57BL/6 mice were given intravenous vehicle, 2 × 10 vector genomes (vg)/kg AAV5-hFVIII-SQ, or 6 × 10 vg/kg AAV5-hFVIII-SQ, followed by either daily oral prednisolone or water.

Gene Therapy with BMN 270 Results in Therapeutic Levels of FVIII in Mice and Primates and Normalization of Bleeding in Hemophilic Mice.

Hemophilia A is an X-linked bleeding disorder caused by mutations in the gene encoding the factor VIII (FVIII) coagulation protein. Bleeding episodes in patients are reduced by prophylactic therapy or treated acutely using recombinant or plasma-derived FVIII. We have made an adeno-associated virus 5 vector containing a B domain-deleted (BDD) FVIII gene (BMN 270) with a liver-specific promoter.