GO-8: Gene Therapy for Haemophilia A Using a Novel Serotype 8 Capsid Pseudotyped Adeno-associated Viral Vector Encoding Factor VIII-V3

Haemophilia A is an x-linked, life threatening bleeding disorder arising from defects in the coagulation factor VIII (FVIII) gene. Current treatment for haemophilia A, the commonest inherited bleeding disorder (prevalence of 1 in 5000 individuals) consists of life-long, 2-3 times/week, intravenous injection of clotting factor concentrates, which is demanding and expensive. In contrast, gene therapy offers the potential of a cure for haemophilia A. In a previous gene therapy study in haemophilia B the investigators showed that a single intravenous administration of a serotype 8 based adeno-associated virus, (AAV8) vector encoding the factor IX (FIX) gene resulted in stable (>6 years) therapeutic expression of FIX without long-lasting toxicity. The investigators plan to use the same AAV8 platform to evaluate a novel FVIII expression cassette, AAV2/8-HLP-FVIII-V3, in patient with haemophilia A. Extensive preclinical studies demonstrate that AAV2/8-HLP-FVIII-V3 leads to long-term, endogenous expression of FVIII in mouse and non-human primate models without toxicity even when twenty-fold higher doses than the proposed starting clinical trial dose were used. Therefore, an open label, Phase I/II dose escalation study entailing a single systemic administration of AAV2/8-HLP-FVIII-V3 in adults (>18 years of age) with severe haemophilia A who have baseline factor FVIII levels of <1% of normal has been designed to establish safety and efficacy of our approach. Dosing will begin at 6x10^11 vector genome (vg)/kg progressing sequentially to 2x10^12vg/kg and ultimately 6x10^12vg/kg in the absence of toxicity. A minimum of 2 patients will be recruited at each dose with a possibility of expanding the dose cohort to a maximum of 6 patients based on safety and efficacy. The study duration for each patient will be 5 years after vector infusion.