Recombinant DNA Advisory Committee - 12/2-3/93 
Dr. Robert Fenton of the National Cancer Institute, NIH, Bethesda, Maryland, explained 
that a substantial amount of information has been published in recent years regarding 
stimulation of immune responses by the B7 antigen. Dr. Fenton said that these 
published murine studies are the preclinical basis for the present human proposal. 
Although in vitro data demonstrating CTL activity was not submitted to the RAC, it was 
noted that these data are probably not critical for RAC review. With regard to B7 
expression in transfected cell lines, only the highest B7-expressing clones were chosen. 
The vector sequences of these cloned cells were integrated into chromosomes at a rate 
of approximately one to two copies per cell. B7 expression is stable in these cell lines 
out to 14 days following lethal irradiation. Regarding the in vitro CTL activity, 
preliminary data indicates melanoma-specific CTL activity. Peripheral blood cells 
obtained from HLA-A2 melanoma patients were mixed with a rotating panel of 3 
transfected cell lines for 6 weeks. Specific CTL activity was demonstrated toward 
melanoma cells. All donor cells have been typed for HLA 
Dr. Fenton explained that the 3 transfected melanoma cell lines will be rotated to 
minimize the risk that patients will not be exposed to an important antigen and to 
specifically boost the A2 response. HLA-A1 patients will be included in this study to 
broaden patient eligibility. Patients will receive untransduced cells in order to serve as a 
control group for assessing the differences in B7 expression. The BPV vector proposed 
for this protocol is similar to the vector previously approved by the RAC for Dr. 
Podack's human gene transfer protocol, except that the early region of BPV has been 
deleted, which contains the transforming genes of this virus. As a consequence, the 
present vector should be safer than the previously approved BPV vector. This deletion 
renders the vector incompetent for episomal replication. The gene is expressed only 
when the vector is integrated and into the target cell chromosome. Most of the vector 
sequences, with the exception of approximately 20 bases at the junction points, are 
included in the assembled sequence. The B7 gene is functional and the likelihood that 
the construct presents any significant risk to patients is small. 
Dr. Sznol explained that all costs associated with patient participation will be covered by 
his institution and agreed to work with his IRB to alter the statement about costs in the 
Informed Consent document. A request for autopsy was not included in the Informed 
Consent document because most patients who are accrued on this protocol will not die 
while participating in the experiment. However, if such a statement is required by the 
RAC, he will include the revision in the Informed Consent document. Dr. Straus 
commented that although an autopsy is often difficult to obtain, an autopsy is preferred 
due to the special concerns that are unique to gene therapy. It is important to 
demonstrate that the gene sequences did not persist in any tissues. Ms. Meyers said that 
several standard items are missing from the Informed Consent document, e.g., request 
for autopsy, request for long-term follow-up, and recommendations for male/female 
contraception. Dr. Leventhal remarked that most patients will probably die at a distant 
location; therefore, autopsy requests should be relayed to local physicians. Dr. Sznol 
agreed to incorporate the RAC's suggested changes into a revised Informed Consent 
document. 
Recombinant DNA Research, Volume 18 
[547] 
