Human Gene Therapy Subcommittee - July 29-30, 1991 
to test the supernatants for viruses that might be generated after packaging. 
Dr. Wilson responded to the comments of the reviewers. He said that this protocol is 
designed to treat the genetic disease FH. Traditional FH therapies include 
pharmacological therapies that involve the modulation of residual LDL receptor levels. 
These therapies cannot be used for receptor-negative patients. Another form of 
treatment involves purging the blood of the LDL. The patient comes in every other 
week for life to receive either plasmapheresis or LDL apheresis. The baseline level of 
cholesterol is reduced 30-40%; however, the original levels return within a week to 14 
days, and there is no permanent change in LDL. Liver transplantation is another 
treatment option for this disease. One patient was subjected to a dual organ 
transplant, heart and liver, based on the hypothesis that reconstitution of hepatic LDL 
receptor status would be sufficient for metabolic correction. As a result of replacing 
the liver, which was from a donor who had normal LDL receptor, this patient's 
cholesterol plummeted. This was an incredibly invasive procedure, and the patient 
ultimately died of complications. At this point, an alternative approach was proposed 
in which genes, not cells, might be transplanted. The hypothesis was that gene transfer 
of the LDL receptor into hepatocytes could provide a sufficient level of metabolic 
correction in these patients. 
Dr. Wilson said that an appropriate animal model, the Watanabe rabbit, was used. 
The gene for the LDL receptor is defective in these animals. The Watanabe rabbit has 
very high elevations in LDL and the same syndrome as the human patients, namely 
clinical death due to diffuse coronary artery disease. A portion of the liver was 
removed and hepatocyte cultures were established. Through the use of recombinant 
retroviruses, the LDL gene was efficiently introduced into these cells. One of the 
limitations is that the cells have to be harvested soon after they have been established 
and reinfused back into the animal. The cells must still maintain their capacity to 
function and persist. The most efficient way to reintroduce the cells is direct infusion 
into the circulation that perfuses the liver. Data were presented from the Watanabe 
rabbit experiments which showed a 30-40% decrease in serum cholesterol levels. No 
deviation from this new baseline level was observed. If a 30-40% decrease in serum 
cholesterol levels could be achieved in patients, this treatment would greatly benefit the 
patient. Experiments with human liver samples have shown that it is possible to 
achieve excellent viability, reasonable recoveries, and sufficient expression of the gene 
using the same organ sample size that would be used in the human trials. 
Dr. Wilson discussed perioperative risks associated with hepatic resection and the 
subsequent reinfusion of the hepatocytes. He noted that Dr. Raper, a co-investigator, 
has extensive experience with hepatic resection. Risks associated with infusion of cells 
into the portal vein are not totally known. In animal experiments, the hepatocytes 
were infused into the portal circulation of a variety of species. There has been no 
evidence of occlusion. The long-term consequences of this gene therapy procedure 
Recombinant DNA Research, Volume 14 
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