Human Gene Therapy Subcommittee - 11/21-22/91 
been submitted by the investigators prior to the meeting. Dr. Royston responded that he 
was not aware that written responses were required to the reviewers' comments and 
added that the investigators had planned an oral response to the questions. Dr. Walters 
stated that the investigators should be given an opportunity to present their data. 
Presentation-Dr. Sobol 
Dr. Sobol stated that this protocol is a Phase I study of tumor immunotherapy using 
autologous fibroblasts that have been genetically modified to secrete IL-2. He 
introduced his collaborators, Drs. Ivor Royston, Habib Fakhrai, and Theodore 
Friedmann. Dr. Sobol described the immunotherapy regimen. Irradiated tumor cells 
and autologous fibroblasts will be transduced with a gene coding for the secretion of IL- 
2. Two biopsies will be taken from patients prior to therapy, a skin biopsy and a tumor 
biopsy. Fibroblasts will be harvested from the skin biopsies and will subsequently be 
transduced with the IL-2 gene. The tumor cells will be irradiated and mixed with the 
transduced fibroblasts. This mixture will be used to immunize the patient against their 
own tumor cells. 
Dr. Sobol described the rationale for the protocol. Although cytokines have been shown 
to be efficacious in providing the cytotoxic elimination of tumor cells, they have proven 
to cause a significant degree of toxicity in vivo when administered systemically. Although 
some investigators have attempted intralesional injections of cytokines to overcome the 
toxicities associated with systemic administration, this approach is impractical for most 
patients. He cited investigators who have attempted to achieve tumor regression by 
genetically modifying tumor cells to express cytokines and added that there are a 
significant amount of data demonstrating that rejection of tumor cells can be achieved in 
vivo by transduction with cytokine genes. 
Dr. Parkman restated his question regarding the amount of IL-2 that is secreted per cell. 
Dr. Sobol responded that there are approximately 30 units of IL-2 secreted per 10 6 cells 
in 48 hours. Dr. Miller inquired as to the equivalent picograms per milliliter. Dr. 
Fakhrai answered that two units of IL-2 is equivalent to one nanogram. 
Dr. Sobol presented data from Dr. Fearon's laboratory using the CT26 colorectal 
carcinoma animal model. Animals were immunized with CT26 cells that were 
transduced with the IL-2 gene and challenged with tumor 2 weeks later. None of the 
animals that received transduced tumor cells developed tumors. The animals that did 
not receive the therapy developed tumors. Four weeks following immunization an 
intermediate level of protection was identified. Dr. Fearon's data demonstrated that the 
spleen cells of these animals were also capable of lysing tumor cells. When these 
splenocytes were analyzed, it was found that specific tumor cell lysis could be abrogated 
with anti-CD8 and anti-Class I major histocompatibility complex (MHC) antibodies. 
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