The Clinical Research Of Using RAAV2/hFIX To Treat Hemophilia B By A Noninvasive Approach Of Administration

Hemophilia B, is a bleeding disorder caused by mutations in the gene encoding blood coagulation factor IX, is one of the most extensively studied disease models for gene therapy. Long-term correction of the bleeding disorder has been achieved in the animal models of hemophilia B using adeno-associated viral (rAAV) vectors through intramuscular injection, the hepatic artery or portal vein administration and so on. But all of these approaches are traumatic. Deliver the recombinant adeno-associated viral vector serotype 2 (rAAV2) into the colonic lumen, it is a noninvasive approach. Previously, we established an experimental basis for gene transfer as a method of treating the disease in mice through colonic lumen infusion of rAAV2/hF IX.To investigate the safety and efficiency of this noninvasive approach in patients with hemophilia B, we selected two hemophilia B subjects. We infused the rAAV2/hF IX vector into two hemophilia B subjects' colonic lumen with the help of fibrocolonoscope. Then observed the subjects' local and systemic symptom and signs; we tested the FIX antigen, FIX antibody and AAV2 antibody by ELISA; APTT-FIX assays were used to detect the FIX activity; we tested the vector genome in the body fluids by PCR.We found that the doses were 3×10¹² vector genomes (vg)/kg to 8×10¹²vg/kg, there was no evidence of local or systemic toxicity up to 1 month after infusion. Circulating levels of FIX reached 6μg/ml and 4.69μg/ml, its activity was 2.27% and 2.63%, respectively, and persisted for about one week. The infusion of the vectors hadn't effect the antibodies to FIX. We didn't found the vector genome in body fluids. We could detect antibodies to AAV2. Humoral response to rAAV2/hF IX was differed from the dose which was infused. The subject who received higher dose could deduce higher antibodies. We could even detect 39.5 times higher at day 24 compared with its initial level in the second subject who received 8×10¹² vg/kg, but the peak then gradually dropped. These results of the noninvasive administration of rAAV2/hF IX demonstrated that administration of rAAV2/hF IX vector by the colonic lumen infusion is safe at the doses tested and result in therapeutically relevant levels of F IX, but future studies were required to achieve long-term expression, high levels and reduce immune responsible.