Safety and Feasibility of Liver-Directed Ex Vivo Gene Therapy for Homozygous Familial Hypercholesterolemia

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Abstract
The purpose of this report was to provide detailed information on the safety and feasibility of surgical procedures associated with the first ex vivo liver-directed gene therapy trial for the treatment of familial hypercholesterolemia (FH). Familial hypercholesterolemia is an autosomal dominant disease in which the gene encoding the low density lipoprotein receptor is defective. Patients homozygous for this mutation have extraordinarily high levels of cholesterol and accelerated atherosclerosis and die prematurely of myocardial infarction. The concept of liver-directed gene therapy was based on the report of normalization of cholesterol levels by orthotopic cardiac/liver transplant in a child with homozygous FH. Five patients with homozygous FH were selected for inclusion in this trial. The patients underwent hepatic resection and placement of a portal venous catheter. Primary hepatocytes cultures were prepared from the resected liver and transduced with a recombinant retrovirus encoding the gene for the human low density lipoprotein receptor. The genetically modified cells were then transplanted into the liver through the portal venous catheter. Numerous clinical, laboratory, and radiologic parameters were analyzed. Elevations of the hepatic transaminases and leukocyte counts and a decline in hematocrit count were noted. Transient elevations of the portal pressure were observed during cell infusion. No major perioperative morbidity—specifically, myocardial infarct, perioperative hemorrhage, or portal vein thrombosis—or death occurred as a result of this protocol. Liver-directed ex vivo gene therapy can be accomplished safely in humans and is appropriate for selected patients.