Minimal Essential Human Factor VIII Alterations Enhance Secretion and Gene Therapy Efficiency

Area of Science:

• Biotechnology
• Gene Therapy
• Hematology

Background:

• Inefficient secretion of human factor VIII (FVIII) limits therapeutic efficacy in hemophilia A gene therapy.
• Developing enhanced FVIII variants is crucial for improving treatment outcomes.

Purpose of the Study:

• To engineer and evaluate a secretion-enhanced human FVIII variant (BDD-FVIII-X5) for hemophilia A therapeutics.
• To assess the in vitro and in vivo efficacy and immunogenicity of BDD-FVIII-X5.

Main Methods:

• Generated BDD-FVIII-X5 by substituting five amino acids in the A1 domain of human FVIII with porcine FVIII residues.
• Assessed FVIII secretion in vitro using cell-based assays.
• Evaluated in vivo efficacy and immunogenicity in FVIII-deficient mice using liver-targeted adeno-associated virus (AAV) vectors.

Main Results:

• BDD-FVIII-X5 exhibited an 8-fold increase in FVIII activity in vitro compared to unmodified BDD-FVIII.
• In vivo studies demonstrated substantially higher plasma FVIII activity levels with BDD-FVIII-X5 delivery.
• Immunogenicity assessments confirmed no increased risk for BDD-FVIII-X5 compared to BDD-FVIII.

Conclusions:

• BDD-FVIII-X5 is a promising FVIII variant with enhanced secretion and therapeutic potential for hemophilia A.
• This variant warrants further development for both gene- and protein-based therapeutic strategies.