A pilot study of ex vivo gene therapy for homozygous familial hypercholesterolaemia

Abstract

The outcome of the first pilot study of liver-directed gene therapy is reported here. Five patients with homozygous familial hypercholesterolaemia (FH) ranging in age from 7 to 41 years were enrolled; each patient tolerated the procedure well without significant complications. Transgene expression was detected in a limited number of hepatocytes of liver tissue harvested four months after gene transfer from all five patients. Significant and prolonged reductions in low density lipoprotein (LDL) cholesterol were demonstrated in three of five patients; in vivo LDL catabolism was increased 53% following gene therapy in a receptor negative patient, who realized a reduction in serum LDL equal to approximately 150 mg dl-1. This study demonstrates the feasibility of engrafting limited numbers of retrovirus-transduced hepatocytes without morbidity and achieving persistent gene expression lasting at least four months after gene therapy. The variable metabolic responses observed following low-level genetic reconstitution in the five patients studied precludes a broader application of liver-directed gene therapy without modifications that consistently effect substantially greater gene transfer.

Liver gene therapy: advances and hurdles

“…These patients had a long-term 6-20% reduction of LDL cholesterol levels and importantly, reconstituted in vivo LDL catabolism. 65 However, no therapeutic benefit was obtained in any patients due to the modest decrease in LDL cholesterol. Therefore, this clinical trial demonstrated the feasibility and safety of ex vivo approach but also its therapeutic inefficacy in treating metabolic liver diseases.…”

“…Consequently, two-thirds of the isolated hepatocytes were lost during ex vivo cell manipulations and transplanted hepatocytes only represented o1% of patient liver mass. 61,65 In addition, cells were also damaged by trypsin treatment, which negatively affected their engraftment and survival ability. Finally, efficacy of ex vivo gene therapy is hampered by cell transplantation because only a limited number of hepatocytes (corresponding to 5% of patient liver mass) can be safely transplanted at one time, and that engraftment and liverrepopulating ability of transplanted hepatocytes is low.…”

“…Consequently, almost all isolated hepatocytes would be re-implanted, so that they would amount for up to 3-5% of the patient liver mass (assuming that a liver contains 3 Â 10 11 hepatocytes for an adult of 70 kg). 65 …”

A novel strategy for in vivo expansion of transplanted hepatocytes using preparative hepatic irradiation and FasL-induced hepatocellular apoptosis

“…4,5 The ability to cryopreserve isolated hepatocytes for immediate availability and to transplant cells from a single donor to multiple recipients makes this modality attractive. Additionally, HT is metabolically less stressful than liver transplantation.…”

“…4 Providing selective growth advantage to transplanted hepatocytes could markedly enhance the efficacy of HT. Therefore, we and others are investigating strategies for massively repopulating the host liver by preferential mitotic stimulation of the engrafted hepatocytes.…”