Somatic Cell Gene Therapy for Hemophilia B

Blood coagulation factor IX is absent or deficient in hemophilia B patients. Current therapy, thetransfusion of human whole blood components, is effective, but it is not prophylactic or free of risk.Our long term objective is the development of a somatic cell gene therapy for hemophilia B. Autologouscapillary endothelial cells from adipose tissue of a hemophilia B patient will be isolated, transduced withthe factor IX gene using a replication-incompetent retrovirus, and grown in a 3-dimensional (3-D)collagen matrix for implantation into the same patient. Capillary endothelial cells in 3-D matrices formtube-like structures that are anticipated to anastomose with the patient's vasculature and becomeperfused with blood when implanted in the patient. In this way, factor IX will be chronically secreteddirectly into the patient's blood, alleviating the clinical manifestations of hemophilia B. In Phase I animalmodels will be used to determine the feasibility of this therapeutic approach. Rat and mouse capillaryendothelial cells (RCEC and MCEC) will be isolated and transduced with retroviruses that encode humangrowth hormone (hGH), human apolipoprotein E (ApoE) and human factor IX. RCECs, transduced withhGH and packaged into 3-D matrices, will be implanted to determine whether anastomosis occurs andwhether hGH will be secreted and detectable in the plasma. MCECs, transduced with ApoE, andpackaged into 3-D matrices, will be implanted in ApoE-deficient mice. Secreted recombinant ApoE fromimplanted MCECs is expected to cause a decrease in the high serum cholesterol in these mice and delayatherogenesis, indicating that therapeutic benefit can result from this approach. Finally, capillaryendothelial cells will be isolated from human adipose tissue, transduced with factor IX, and packagedinto 3-D matrices. Factor IX production by these cells, together with the animal studies, willdemonstrate the feasibility of this therapy in humans.