Human Gene Therapy Subcommittee - 11/21-22/91 
determining IL-2 serum levels; however, it is not anticipated that IL-2 serum levels will 
be elevated above pretreatment levels. Dr. Leventhal noted that if systemic IL-2 levels 
are not expected, than local IL-2 production is critical. 
Dr. Leventhal said that the investigators should provide a statistical section that defines 
success, failure, and stopping rules in terms of genetic manipulation. The possibility of 
enhancing tumor growth by ID2 transduction should be discussed. In addition, the 
number of patients proposed for the study should be clearly stated and rationalized. If 
the tumor burden in these patients increases significantly, how will the investigators 
determine if tumor growth was induced by IL-2 production or was part of the natural 
course of disease? 
Dr. Walters suggested that several HGTS members should create a detailed list of the 
preclinical studies that would be necessary to perform prior to the investigators' 
returning to the subcommittee for approval. Dr. Royston reminded the HGTS members 
that preclinical studies have already been detailed in the primary reviewers' written 
comments. 
Dr. Royston said that he was concerned about Dr. Epstein's written comments regarding 
the importance of using primary mouse skin fibroblasts in the preclinical model as 
opposed to a fibroblast cell line. Dr. Miller stated that primary fibroblasts are critical 
for the model. Balb C tissue culture cells will form tumors in mice. Dr. Royston said 
that they had not observed tumors as a result of these cultured cells. Dr. Miller asked 
how long the animals were observed. Dr. Royston stated that the animals had been 
followed for as long as three weeks. Dr. Miller said that tumors develop in mice after 
one to two months with tissue culture cells. 
Dr. Erickson stated that primary fibroblasts cannot be obtained from an adult mouse. 
Dr. Miller replied that a primary fibroblast strain can be obtained from an adult mouse. 
Dr. Royston agreed that he and his colleagues would make an effort to obtain an early 
primary fibroblast passage for the preclinical experiments. 
Dr. Sobol asked if in vivo IL-2 expression experiments are performed in animals, would 
patient biopsies still be required for the human study. Dr. Leventhal noted that 
immunotherapy has been repeatedly proven effective in murine models but not yet in 
humans. Patient biopsies will be necessary to assess gene expression. Dr. Royston 
reminded the HGTS members that human experimentation is of ultimate importance. 
How much preclinical data is necessary? Dr. Parkman said that needle biopsies do not 
even require anesthesia because of the small specimen size. Performing reverse PCR to 
assay for IL-2 gene expression will require very few cells. 
Dr. Parkman said that preclinical data should be provided in the following areas: (1) use 
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